I really wish a Apple or another major OEM would integrate CO2 monitor into watches or smartphones. Suddenly, everybody would be aware of the CO2 level in the room, get alerts, etc. and the problem will just solve itself.
There are so many rooms, classrooms, movie theaters and other places with poor ventilation where you just feel dizzy, or fall asleep, not knowing it was just due to lower oxygen levels in your blood. Raising awareness is the only real solution.
> I really wish a Apple or another major OEM would integrate CO2 monitor into watches or smartphones
CO2 levels are locally elevated in the area where you exhale. Someone sitting at a desk with their hands on a keyboard exhaling through their nose would be producing a directed stream of elevated CO2 straight at the sensor on their wrist. Same thing if someone puts their phone on their desk.
Even with the IKEA and other cheap sensors that are becoming popular, there is a learning curve where users discover that putting it on their desk right in front of where they’re breathing produces higher numbers than having it even 5 feet away.
The false positives from having a CO2 sensor that close to everyone’s face would be causing unnecessary alarm all over.
> There are so many rooms, classrooms, movie theaters and other places with poor ventilation where you just feel dizzy, or fall asleep, not knowing it was just due to lower oxygen levels in your blood. Raising awareness is the only real solution.
If someone is falling asleep in this many different places I would suspect undiagnosed sleep apnea or another condition first and foremost. Spaces like movie theaters have very high volumes of air due to their size and commercial building HVAC has much higher standards for air circulation than even your home. If someone was falling asleep in so many different places then the most likely common theme is that person and it should be checked out!
This is another reason why putting CO2 sensors on everyone’s wrists would be a mistake: It would start getting blamed for every vague condition people experience. This has already happened with wrist-worn heart rate monitors. My friends in the medical field see people all the time who come in with vague complaints and they’ve self diagnosed as being related to their heart because they can see their heart rate now.
You also have the wrong idea about what elevated CO2 does. It doesn’t reduce the oxygen levels in your blood. It makes it more difficult for your body to expel CO2, which can produce subtle changes in many processes.
> CO2 levels are locally elevated in the area where you exhale.
That's the same area we inhale from... Wouldn't be right to measure there then? It's not like we're interested in the amount of CO2 on the ground (in this discussion)
No, because the studies that establish the levels correlated with cognitive changes use ambient CO2 levels. Not with a stream of air directed, maybe, from your nose to your wrist.
It is not possible to come up with a different baseline for wrist-worn monitors because the measurements could change significantly based on even small factors like the position of the wrist or smartphone.
Because the thresholds everyone gets from the studies were not measured in that location.
It would be like the weather station telling you it was 160 degrees outside because they put their thermal sensor on the asphalt, but you wanted to know the air temperature.
> There are so many rooms, classrooms, movie theaters and other places with poor ventilation where you just feel dizzy, or fall asleep, not knowing it was just due to lower oxygen levels in your blood. Raising awareness is the only real solution.
Not wrong, but it is perhaps worth noting that there are already standards for proper ventilation. Generally you're looking at 5–10 cfm/person (2.5-5 L/s), depending on the facility and purpose of the room; see Table 6.2.2.1 in ASHRAE Standard 62.1 for the US:
Maybe set up a monitor, but if the room/facility has recently been renovated and meets modern (>2013) building codes, this 'should' have already been taken into account.
Whenever I travel, I bring a CO2 meter with me. It’s amazing how often the air is bad. Often in unexpected places. My meter hit 3100 in an uber once. I didn’t even notice until I got to my hotel room and looked at the data log. It was a fresh, hot day outside. The uber had windows closed and AC on. I bet he had no idea - but he was driving with significant cognitive impairment. Takeoff and landing in planes are always the worst. If you get sleepy as the plane is taking off, it’s not you. The plane’s ventilation doesn’t work properly when the plane is stationary. So before a plane is in the air, they often hit 2500.
Take it outside, as long as it measures 400-450 it's probably good.
Metrology calibration is necessary if you want accuracy better than 10%, but most of us don't care at all about that, instead we care about increments of 200ppm or more.
Local factors can make your CO2 fluctuate by 200ppm. If you're near a busy road with not a lot of wind 600 ppm is possible. But it's not that important if you open your window at 1000 ppm or 1200 ppm.
Building codes that address this are wonderful, however:
- Plenty of people live or work in older buildings, where are not up to standard. For example: my office probably violates the air quality sensibilities of the Victorian era, which is when it was originally built.
- Equipment breaks down, isn't operated properly, or wasn't installed correctly. Having monitors that measure air quality is an extra check. While you may not be able to get direct action upon a consumer sensor, it can help you push for action.
I've been in buildings of varying quality over the years. I've seen how it takes time to get people in to do air quality testing. Heck, I saw the government claim that the air quality was acceptable in schools during the pandemic because the schools had passive ventilation systems. That meant they could open windows. (To be fair, the air quality in most of those buildings was probably fine since that was how the buildings were designed. That said, such standards make it easy for some buildings to slip through the cracks.)
This is correct, but there's still a lot of opportunity to do better.
I've been involved with the build out of several office spaces in new and old buildings. We always took this sort of thing seriously and measured each room independently for a week (many at a time) ensuring we accounted for periods of high occupancy.
This let us tune the HVAC systems to operate more efficiently, ensuring comfortable temperatures and air circulation. Every time I've seen this done there were structural deficiencies that required remediation, some times it meant adjusting duct work.
Most modern office buildings are designed to be a platform for constructing spaces, as spaces usually evolve and change between leases and tenants. They're designed to accommodate this sort of thing.
However I've found that no build out nails this the first time. It's very hard! Often times things look fine but once you get people in the space things change drastically. It requires time and effort to address.
Several of my offices had such good air that I'd prefer being there over pretty much anywhere else -- even outside on poor AQI days.
I've also found that a lot of offices don't do any of this and their air quality is noticeably poor. And lastly I've found that the oldest buildings, including schools -- and I'm talking really old -- have very good air because they are so incredibly leaky. They're usually harder to cool and heat, though.
I think modern domestic houses its the opposite. At least in Netherlands insulation is such a strong focus, due to climate change I think, that modern appartments have terrible ventilation
Stayed at a beautiful new house in Finland, with five people instead of the usual two, the CO2 detector intermittently went off while we were sleeping. Which the hosts assured us was a faulty detector. They also spoke to how extremely energy efficient the house was, to us it seemed like there wasn't enough ventilation, to improve the insulation. Against their wishes, I slept with all windows fully cracked, which was only ~2 inches due to the "efficient" design.
> I think modern domestic houses its the opposite. At least in Netherlands insulation is such a strong focus, due to climate change I think, that modern appartments have terrible ventilation
The link I pointed to is all about ventilation, so just because people ignored an important component of building science, and focused on one aspect, does not invalidate it.
And while climate change is important and using efficiency to deal with it is useful, the thermal control layer is actually the least important of the four:
'Bulk' water (precipitation) and moisture can cause deterioration of the building materials (rot, crumbling), and also mold, which has its own health effects. Leaky houses can often blow conditioned air at much faster rates than thermal leakage.
How modern? We built or house in Belgium in 2016, and it was completely sealed, very well insulated, but the air quality was good because we had mechanical ventilation. Clean air blown in, stale air extracted which then went through a heat exchanger.
The only issue this house had was it overheated. We had glass facing south. Even in winter it instantly became too hot.
Energy recovery ventilation is the answer to this.
HRVs only deal with temperature, but then you have humidity that is non-controlled: moisture coming in during the summer, and getting vented out in the winter (too-dry air coming in).
A friend of mine recently moved to a modern apartment, built only a few years ago to a very high isolation standard (Germany). I stayed over night and slept on his couch, the air got really really dry and stuffy. It was really uncomfortable.
I think the issue is that the common tech requires sensors in an air-chamber. E.g. NDIR works by firing IR at a frequency that is absorbed by CO2. A sensor on the other side either measures the amount of IR light that got through (optical NDIR) or pressure/sound waves (photoacoustic NDIR). I guess that it's hard to use any existing sensors, because they are relatively large and probably water could easily get into the chamber.
Would be extremely cool if Apple, Samsung, and others can crack this, though I think they'd have done it already if it was easy.
Oxygen sensors used in car catalyst systems use a different effect based on electrochemistry. I see no reason that couldn't be minuaritized to grain-of-sand size.
The question is if oxygen levels are as good an indicator as CO2 levels... I suspect not.
Based on numbers, O2 concentration is probably not a good indicator.
Clean air contains about 20.9% O2 and 0.04% CO2. At 2000 ppm CO2, which according to the author is bad enough to impair judgement, that's 0.2% CO2, it that CO2 is the result of respiration, it means that about 0.2% O2 was consumed, so that's a drop from 20.9% to 20.7%, a very small difference. 20.7% is not low enough to have a significant effect, the CO2 itself is the problem, not the drop in O2. And using O2 concentration as a proxy for CO2 doesn't look reliable to me: the difference is small and other things, like humidity can affect O2 concentration.
As for the sensor, O2 sensor in cars compare the O2 concentration between the outside air and exhaust gases, it needs outside air as a reference, but what you are measuring is the outside air itself, you don't have that reference.
CO2 concentration doesn't start at zero, and by coincidence, if CO2 production is 80% of oxygen consumption, consuming 0.2% oxygen results in 0.16% CO2, add it to the base 0.04% and you get 0.2%.
It looks that some O2 sensors that don't require a reference have been used (titania sensors) but even though they have some advantages, they are less precise and mostly obsolete.
I had a project miniaturizing nasa tech for detecting hypoxia with o2 and CO2 sensors. It used a phosphorescent dye that changed a delay flash (ie you blinked a light, the dye would absorbed and blink back after a delay) based on temp and o2.
CO2 was measured with infrared but water also absorbed it, so you need to heat things up enough to not have water. It can be small, but not watch small.
> CO2 was measured with infrared but water also absorbed it, so you need to heat things up enough to not have water. It can be small, but not watch small.
Can't you just measure CO2 "naively"; but then also, separately, measure rH; and then use the rH value to grab a research-calibrated LUT to pass the raw CO2 value through?
(I presume this is why all the little standalone CO2-sensor boxes you can buy also have rH displays. They're measuring it anyway to normalize the CO2 value, so they may as well make it a feature and display it.)
Electrochemical pile style oxygen sensors continuously deplete themselves whether actively measured or not. Common smart home oxygen piles have a fixed lifetime of a few years, and they're quite sizable (probably about as much volume as a whole smartwatch). Putting the same chemistry in an even smaller package would likely result in lifetime measured in hours
I assume this is because of diffusion of materials at elevated temperature. The sensor would, I think, require a lower temperature than an electrolyzer, since the current would be much lower. But it would be best if lower temperature solid oxide electrolytes could be discovered.
The ones in cars need to be heated up quite a bit in order to work, and you still need reference air. Otherwise, I'm pretty sure that CO2 isn't a problem but rather an indication of a lack of oxygen in the first place, so it technically could work... just not if you're measuring the environment itself.
This is in theory not a problem: getting an oxygen sensor to 700 degrees if it's a tiny spec on a chip is not necessarily hard or would even require a lot of power.
But...oxygen concentration is essentially indepedent of CO2. We measure CO2 at part per million levels, whereas O2 is 20% of the air.
(In that context CO2 is surprisingly toxic given that 1000 ppm can impair mental acuity).
The goal of a gasoline engine's sensor is to accurately and precisely measure the point where O2 concentration reaches zero, so ambient air levels are not quite as relevant.
> I think we use them as a proxy for o2 levels (same as our bodies do).
Probably. ISTR that depriving a body of oxygen results in a different response than overloading the body on CO2. It's why if you completely displace all air in the room with CO2, people choke, panic, etc, but if you use Nitrogen, people just keel over dead without realising it.
The evolved response to CO2 is part of the human body’s ability to filter and remove CO2 via the respiratory system. AFAIK we don’t have similar capacity for Nitrogen because it’s not a primary waste product of that system.
Dissolving CO2 in water creates some carbonic acid (H2CO3) that will decompose back to water and CO2 when the CO2 concentration drops. Blood has a fair bit of water, and carbonic acid is much easier to detect than oxygen or nitrogen gas
We evolved to detect CO2 because that's by far the easiest thing to detect that's still a reasonable proxy for the performance of our respiratory system
I'm pretty sure that in a room where we replaced nitrogen with co2, we would be dead even if O2 concentrations were the same. Something about partial pressure. I notice AI explanations agree with me (not going to copy and paste them).
It's about pH. CO2 creates carbonic acid when it dissolves in water. Your blood pH, in turn, controls how much you feel like you need to breathe. So with high CO2, your respiration rate slows down, and that can lead to low oxygen levels.
Note that the physiology and biochemistry of this is complicated (e.g. blood is a very good pH buffer and it's actively regulated by kidneys etc) and it's very much a nascent field of research, so I think AI will be overconfident and hallucination-prone.
Source: I worked in high-co2 caves for my PhD so have read about this a lot. I always carried a CO2 monitor. Our rule was to get out if we saw 20,000 ppm or greater. I spent thousands of hours above 10,000ppm.
My medical student flatmates were talking a lot about acidosis and alcalosis :)
It was the first time that I heard about them. These basically never happen if your body and environment are halfway decent, but they are important in exceptional situations.
Pretty sure I learned the effect was the opposite (high CO2 --> slower respiration). Note that that was ~15 years ago when I would have read that. Maybe I just misunderstood, or thinking has changed.
edit: reading now I see I was wrong about this. Thanks for the correction!
You are right about the pH implications, but respiratory acidosis leads to hyperventilation, not hypoventilation. CO2 will kill you regardless of oxygen supply.
If that’s the sole source and the application does thoughtful analysis it could determine that there are sections of the room that are better than others, yes
I guess the problem is with the price of the sensors. Just look how expensive the Aranet 4 home shown in article is. There are worse devices for less like the IKEA alpstuga. I also don’t know how much electricity they pull.
I would hesitate to say the IKEA is worse. Inside the IKEA is a reputable Sensirion all in one sensor module. It's much cheaper and smaller because the CO2 sensor in it is using different (newer) technology that only released a few years ago from Sensirion.
(Upd: the IKEA does have lower accuracy, with ±100 ppm instead of ±30 ppm. From the SEN63C datasheet)
Worse specs? Sure. Worse value? I don't think so. Worse accuracy? Perhaps not either.
A price of 30 EUR makes this sensor really easy to pick up. For the same price as one Aranet (~180 EUR) the typical household can place a sensor in every room of the house. Which provides far more accurate readings for the whole house than just one high-end sensor in one room.
I have one IKEA Apstuga on my desk, sitting right next to a good CO2 monitor.
Since Apstuga uses worse approach (heat) rather than light as the good sensors, it diviates around +/- 100 ppm. For example the correct CO2 is 610 ppm and IKEA's sensor shows 552 ppm with is reasonably close. So the trend will be correct and the values will not be.
But when it goes over the safe limit it should be enough to decide to ventilate.
No, it is crap. Yes, it is Sensirion, but it uses a thermal conductivity sensor, which is a very indirect method of measuring CO2. One part of the sensor emits heat and the other senses it and the idea is that heat transfer changes with different CO2 concentrations. However, a lot of other factors influence this as well, such as ambient temperature/humidity (which is why the sensor incorporates measurements from an SHT sensor), but also gas mixture, etc. You only get good readings at lab conditions. Even below 1000 ppm, I would often see readings that are 300 ppm from more expensive, known-good CO2 meters.
If you want a CO2 meter on the cheap, either wire up an optical NDIR sensor like the SenseAir S88 (22 Euro) up to an esp32, which is possibly the best sensor you can get for the money (slightly cheaper version of the sensor that the AraNet4 uses). Or if you want something standalone with a display, get the SwitchBot Meter Pro CO2 for ~50 Euro, which uses a photoacoustic NDIR, but is still miles better than the sensor in the ALPSTUGA. Can also be hooked up with HA through an ESPHome BLE proxy or with the SwitchBot Hub.
You can find a comparison of the IKEA sensor with other affordable sensors here:
(Upd: the IKEA does have lower accuracy, with ±100 ppm instead of ±30 ppm. From the SEN63C datasheet)
You forget to mention that it is ±100ppm plus ±10% of the ambient ppm, which makes a big difference. At 1000ppm it's ±(100ppm + 0.10*1000) = 200ppm and that's only in an environment with 25C, 50% RH, and 1013 mbar. So, that does not tell you much, given that thermal conductivity is very sensitive to environmental factors.
No, it's not. You generally want to ventilate an office when you reach 1000ppm, but then the IKEA will often warn you already at 700ppm. 700ppm is fine.
"Generally" is a vibe measurement to begin with. You won't notice any difference at all between 700ppm and 1000ppm. It's once you start hitting 2000ppm you are getting noticeable brain fog.
Had bad ventilation in my old apartment (built 1888) so got a co2 monitor. Started feeling the effect at 1100-1300ppm, so would open it in home assistant and check, never below and never above really. During winter when it was -10 so couldn't keep the window open all the time.
I disagree. I feel a very steady and progressive deterioration starting at 600 ppm. It becomes significant at 800 ppm. The studies back up the latter threshold.
You're not wrong, but indoor CO2 at these sub-1000 levels is a useful proxy metric for bioeffluent VOCs which are an objectively tiring subset of total VOCs. Ventilation lowers both. This explains the observation better than nocebo theory. See https://www.aivc.org/resource/effects-carbon-dioxide-and-wit...
You would not notice a difference if you weren’t checking the CO2 ppm. You primed your brain to ‘feel’ the effects of higher CO2 by reading a study and are experiencing the nocebo effect.
If it makes you feel better I don’t see a problem with it.
Indoor CO2 is likely overrated here at these sub-1000 levels but it's a useful proxy metric for bioeffluent VOCs which are a tiring subset of total VOCs. Ventilation lowers both. This explains the observation better than nocebo theory. See https://www.aivc.org/resource/effects-carbon-dioxide-and-wit...
Have you looked at the prices of meeting room furniture? A $200 meter is not a significant cost measured against what it costs to furnish the room in the first place. It only becomes significant is you treat it as a line item disconnected from the room it's in
There are good $50 Euro meters. Besides that, I am not sure if that is true, at my wife's workplace, they put high-end CO2 meters in every larger room where multiple people meet. Admittedly, this was during COVID, so a lot of organizations were using CO2 levels as a proxy for finding whether a room was properly ventilated.
Presumably there is still the need to ventilate. So the concentration can also be measured more centrally. That is how the mechanical ventilation unit in my house works. For both humidity and CO2.
I got the ikea sensor, I’d say it’s way more accurate than you need for personal use. I wouldn’t use it as a scientific instrument but it’s well good enough to see if the room is ventilated enough.
I was shocked to see just how fast CO2 climbs while in a room, and how just opening the window just a crack was enough to restore the room to baseline co2.
The thing runs on usb 5v so the power consumption is negligible. It also plugs in to home assistant great.
I have HA send me a notification to ventilate my office when the air reaches 1000ppm CO2. The IKEA ALPSTUGA is often off by 300ppm even under 1000ppm. If I'd use it, I'd be getting notifications at 700ppm.
It is a thermal conductivity sensor, which is a very indirect way of measuring CO2 and is very sensitive to environment factors. You only get somewhat good readings in lab conditions.
Don't by the ALPSTUGA for anything but very rough trends, there are much better affordable options.
I notice that thinking becomes less clear when going above 1000ppm, so I let HA send a notification at 1000ppm. With ALPSTUGA it would send already at 700ppm. By the way, above 1000 the divergences become even larger due to the inaccuracy also being 10% of the ambient CO2 concentration (in optimal circumstances, probably larger IRL). So, suppose you want to be notified at 2000 ppm, the IKEA sensor might already do so at 1500 or 1600 ppm and it continuously drifts, so it's not like you can use a particular offset.
Besides that, what's the point? There are much better meters in a similar price class. As an additional benefit, they can last months or up to a year on two AA batteries.
I'm using a bunch of IKEA's "smart home" stuff, all via Zigbee+HA, works great. Look for the Zigbee icon on the package, and the pairing for Zigbee vs their own home controller might have slightly different pairing sequence on the device, otherwise it just seems to work.
They recently overhauled their lineup and replaced all Zigbee devices by Thread + Matter. Some of the new devices (mostly those who support TouchLink, e.g. some of the lights) have a secret pairing mode with which you can use them with Zigbee, but it's only a subset of the new products.
> They recently overhauled their lineup and replaced all Zigbee devices by Thread + Matter.
Uuh, seems not keeping up with social media finally backfired. That sounds horrible! So far IKEA been a great experience when it comes to HA+Zigbee stuff, and I started buying stuff relying on they'd keep just keeping up with that, really sad to hear they've changed course.
The "secret pairing mode" stuff sounds the same as currently/before though, but they only do so for a subset is new and hope they again change their mind.
Thread is significantly better. Zigbee relied on proprietary hubs and apps or hacky work arounds. Matter over thread devices don't need a brand specific hub or app. You can literally control the new ikea products direct from a modern iphone which includes a thread radio, no hub, server or app required.
If you already own the ikea hub, they secretly put thread radio in it which was just sitting unused in preparation for this range.
It's complicated. Matter over Thread is indeed nice in that it you only need generic Thread and Matter servers. It also makes it easier to share credentials between ecosystems. Thread itself is also a pretty nice standard technically.
There are also strong downsides though, one is privacy and future cloud lock-in. Zigbee is fully local. Previous Thread standards added the option for NAT64 so that Thread devices can access the internet and there were some Thread + Matter devices that already require internet access for full functionality (IIRC some Nuki smart locks, but I might misremember). However, Thread 1.4 also adds support for Thread devices to get a globally routable IPv6 address. The Thread 1.4 whitepaper is pretty blunt about what this enables:
Simplified Cloud Integration: Thread devices can now seamlessly connect directly to cloud services, enabling remote control, monitoring, and over-the-air firmware updates.
The fact that Thread and Matter are strongly pushed by Google, Apple, etc. should tell you enough.
Now, a TBR may simply allow you to disable NAT64 or globally routable IPv6 addresses (e.g. Home Assistant's addons), but many consumer implementations don't. E.g. the Apple TV is a Thread Border Router and does not allow disabling NAT64, so Thread devices can access the internet, send analytics, and can be cloud-controlled.
Also, the ecosystem is still pretty immature, as a result of which you can encounter issues, typically resulting in unstable device connectivity. E.g. TREL does often does not work well. Apple has some hacks to fix most of the issues, but it only works well between Apple devices. So it's generally the best to avoid combining multiple TBRs into the same network.
Better than what already exists and is deployed? I dunnno, hardware already in use always beat "hardware conceptually better but I don't have it", that's why Zigbee is better, for me. Protocols much like everything in the world, isn't correct/incorrect or universally "better", it's all down to use cases.
Personally, as someone who started to rely on IKEA providing Zigbee devices, Thread is obviously worse, because 100% of the devices I have are already Zigbee and not Thread.
Ikea preemptively sorted this out by putting thread radio in their hubs years before rolling this out. There's also thread radios in the latest chromecast, apple tv, and loads of other products. If you have a single thread border router in your house from any brand you'll be able to connect to any thread device from any brand. Phones can also directly control thread devices without needing any network or hub.
It's a vastly better system and the transition period is so smooth because the smart home companies have been deploying the thread hardware for years before anyone started using it.
smart home companies have been deploying the thread hardware for years before anyone started using it
Also worth mentioning that many modern Zigbee radios can also be Thread thread radios using different firmware. There are even multi-PAN radios that can do Zigbee and Thread at the same time. Some smarthome hubs use multi-PAN (e.g. Homey Pro), but it's generally recommended against now because of lower reliability.
The same applies to devices, e.g. some of the new IKEA devices work over Thread or Zigbee (Zigbee pairing is triggered using a non-documented sequence, presumably they added support for TouchLink). Or e.g. the Aqara FP300, which can be flashed with Thread + Matter or Zigbee firmware. It works because the same radio can be used for both protocols.
Yeah, I bought a bunch of INSPELNING smart plugs when they were clearing out the inventory. The new GRILLPLATS switches are more compact though, which is nice.
I don't think power use is the issue. I have this cheap CO2 sensor: https://www.domadoo.fr/en/devices/5882-heiman-zigbee-air-qua...
which draws 0.5W. This includes thermometer and humidity sensor, Zigbee transmission, and acting as a Zigbee router, but it gives us an upper bound.
It also measures continuously (picks up someone breathing on it within 10s), which is overkill. A phone could measure CO2 levels once every 10 minutes which would average under 0.01W, so that would work.
However, this assumes the sensor would fit in a smartphone, which is not a given. And these things need air flow. And they also wouldn't work while the phone is in a bag or a pocket.
>A phone could measure CO2 levels once every 10 minutes which would average under 0.01W, so that would work.
Not sure about that, at least NDIR sensors have to be at certain elevated temperature to work and they do some preheating when you turn them on from standby.
So it's not possible to just measure less often as then energy would have to be spent on heating the sensor.
Ruuvi Air[1] seems to be close to the middle in both price and CO2 measurement accuracy between aranet4 and the IKEA device. I don't have personal experience with Ruuvi Air specifically, but have been using their cheaper Ruuvi Tags (that don't measure CO2) for temperature, humidity and air pressure measurement at home and office.
Is it a tually lower oxygen in the blood that's the problem, or higher co2? I'm not sure if having high co2 automatically implies lower oxygen, I have no idea at all but feels like it may not necessarily be strictly. Linked. Also, are the cognitive issues of low oxygen the same as high co2 or do they produce different effects?
You'd have to raise awareness on every single person in the room and them sustain pressure to the organization in order to have proper CO2 levels in the room/organization.
And then you have to align every other person on every other organization to do this as well and hope for the best.
Or, you can do the right thing and have the state introduce regulations
I don’t think that’s right. If people have an easy way to measure the levels, and they can see something on their phone like ‘you spent 8 hours today above 2000ppm CO2’ then the room will care a lot more than it did before, and people will be able to quickly see whether they have improved things. At my employer, I think it took us around 1000 employees until we randomly hired someone who happened to care a lot about CO2 levels and I think they managed to cause a decent increase in the amount that the company cared / thought about levels (this was around the end of Covid though so part of this may have been due to using CO2 levels as an indication of insufficient ventilation/air filtration).
Depending on the state, newer buildings do have regulations on air ventilation and quality.
The rooms being discussed here are mostly ones which would have been built before this was taken more seriously. Classrooms, older office buildings, etc.
NYC is full of buildings which would never pass any code today but are still happily occupied. It’s a trade off, I think.
I can just imagine the horrors and skin crawls that your last sentence has evoked in some people's minds. Not the state!!
But seriously, so much care needs to be taken here. OK, well "care" at least. Employers certainly would benefit from scrubbing CO2 from the air, in terms of productivity. I'm willing to bet that with central air it would be quite easy, and even with heat and AC off, lots of places still circulate the air regardless.
So the central place to scrub is already there.
But then you have other issues. Such as, will your body adapt to 8 hrs of reduced CO2, and then you become torpid and barely awake when not at work. Such a horrid thought, that is to me. And what if employers learn that the tiniest boost of O2 helps too! Now your body becomes accustomed to that, and what are the long term effects there?
I can personally envision myself being concerned. I guess the legislation could be crafted to "the same CO2 levels found just outside of downtown city core" or some such blather. Maybe even same for O2. So that you're at least pegged to something normal for the area.
Maybe that's where the state could come into play. A simple, highly accurate monitoring station which has an API to be polled.
Come to think of it, CO2 and O2 rates fluctuate during the 24 hour cycle. Trees need O2 to live, but only produce O2 during the day. And so differing amounts of light might mean up and downs in these numbers. It may be another circadian rhythm. Getting it the same as in a nearby forest, might be the healthiest thing of all.
In practice, one would use energy recovery ventilation to exchange air with outside rather than a CO2 scrubber (not clear if you actually meant a scrubber).
I have been in some office buildings in United States which had CO2 monitors in each meeting room, and the ventilation would engage to control CO2 below a set level. We would entertain ourselves by exhausting our lungs onto the sensors to trigger the ventilation system.
I should have said it more clearly, I just thought HN would take this stance regardless. If you tell an employer to ensure CO2 levels, and it shows an improvement in productivity, employers may think "Hmm. Let's improve this further!" and add O2 as well.
In terms of outside air, a lot of US cities I think would not benefit from that, all that much. Especially during certain parts of the day, with a lot of smog.
But regardless, all that entered my mind was "Once employers are required to add any form of scrubbing, and perhaps O2 injection, they'll over do it for optimal employee output." Regardless of whether it's helpful once the employee leaves the workplace.
I'm not against this, I'm just actually saying the regulation should be locally defined.
Controlling indoor CO2 is important, but it's a proxy metric for the escalation in indoor bioeffluent VOCs which are a tiring subset of total VOCs. This is why scrubbing indoor CO2 will by itself never produce the pro-cognitive result you want. See https://www.aivc.org/resource/effects-carbon-dioxide-and-wit...
Scrubbing indoor CO2 is sensible only when you want to go below the outdoor CO2 level, not at levels above it.
It is not that complicated. You need to introduce CO₂ threshold levels that make sense from a medical standpoint. Then you need to enforce them in the same way other basic environmental regulations or worker rights are enforced in regions of the world where these work.
The main question is: If your workplace, city, whatever forces you to work or live in an harmful/unhealthy environment, do you have any realistic course of action to improve the situation? In the US you would call this (gasp) regulation, I would call it a basic human right.
If we talk about stairways, nobody complains about building regulations that mandate handrails. CO₂ levels are not totally different.
And I believe the accuracy is also not great on these cheap ones. The product in the OP's photo costs $200 where I live! And ISTR finding the sensor itself contributes a lot to this cost.
IIUC they also need fans. The one I have in my home has one that's actually integrated into the sensor unit.
CO2 and all other air quality indexers have to be very carefully calibrated regularly. It's not some slop you can just throw into a consoomer cheap iot device.
Article author completely ignores this for the obvious reasons.
For the purposes of indoor ventilation monitoring you can calibrate by occasionally exposing the sensor to fresh air. Either taking it outside or just the room not having people in it. The sensor will treat the lowest reading it gets as 400ppm since this is what outdoor air is.
A sensor mounted in the office will get calibrated every night when the office is empty.
The outdoor CO2 is rising every year. It is not fixed at 400 ppm. The calibrations you speak of are fake. A good sensor can be expected to remain within 10% of reference for ten years.
You don't need to routinely calibrate a good device at all for that purpose. It already will maintain a reading within 10% of the real value. If it's not doing that, it's a bad device. It's very possible your calibration process will actually miscalibrate it and increase the error. Already the outdoor CO2 level is 430, not 400, so you'd be introducing at least a 7% error by calibrating it to 400.
What I do at home is I have multiple meters bought over the years, not all at once. If one of them is too deviated, I can replace it, but this deviation has never happened in the last five years. It did happen once about ten years ago with an old model.
Not really. For ventilation purposes, a good sensor remain within 10% variation for nearly ten years. We are not running a controlled science experiment here.
I don't think that's true at all. Capnography, the measure of carbon dioxide partial pressure is wholly separate from pulseox:
> Pulse oximeters have some limitations. They can only employ light at two wavelengths. Thus the devices can only distinguish between hemoglobin and oxygenated hemoglobin. When carboxyhemoglobin and methemoglobin are also present, there are two additional wavelengths required for differentiation. In the presence of elevated carboxyhemoglobin levels, pulse oximetry overestimates the true saturation of oxygen as carboxyhemoglobin binds with a higher affinity than oxygen. In the case of carbon monoxide poisoning, the absorbance spectrum of carbon monoxide is very similar to hemoglobin, which results in a falsely high level of oxygen (overestimation of oxygen saturation) ...
I don't think that's safe to assume at all, for two reasons:
1. CO2 has effects on the human body of its own that aren't simply a lack of oxygen, and vice-versa. [0]
2. The baseline proportions involved aren't close, so even doubling CO2 isn't going to show up easily as a large swing in in oxygen%.
For example, the article references a study where the CO2 proportion going from 0.04% -to 0.25% correlates to mental problems.
Even if the watch could sample atmosphere directly, is it sensitive enough to detect a shift from 21.00% -> 20.79% oxygen?
As it's estimating oxygen in the owner's blood, it might not detect anything different at all... not if the owner's body has already compensated by breathing harder or by "underclocking" their brain to make dumber decisions.
> The article references a study where the CO2 proportion going from 0.04% -to 0.25% causes mental problems. In other words, a difference in 0.21% of the air.
I'm finding that pretty difficult to believe, to be quite honest with you.
And before you say "aha, carbon dioxide brain fog!" consider that I'm about a mile from the sea with a 40mph onshore breeze. This air is about as oxygenated as it gets.
It makes a lot of sense actually. You get severe symptoms when CO2 makes up only a couple % of the air. And can become fatal at like 5%. There’s not like a hard line where you suddenly die, it’s a gradual thing. It very much makes sense that we’d notice minor symptoms at a few thousand PPM when it only takes like ten thousand to feel it severely.
I got a monitor as we had an old apartment with bad ventilation. When I started feeling it I would check and it was always around 1200ppm and would open a window for a bit. Outside air is around 420ppm, but that's not the problem, enclosed and badly ventilated rooms are if you spend a few hours in there.
I’ve had a Co2 monitor for years. I get headaches from increased Co2 levels plus the lethargic state. It’s been revolutionary - including on long drives where it’s def saved me from crashing.
Personal opinion, you can see cognitive decline at 1000 ppm. Not “ur a zombie” but it’s there. Airflow has vastly improved my life.
Another personal opinion - the coporate stupidity and inane behavior we all see tracks back in part to Co2 levels turning people into quasi zombies. It’s a lot easier to just not care, and things don’t click like they should, when in higher Co2 environments - pushing everyone to rote, process, unthinking approaches. Sounds familiar?
As a high school teacher, I first noticed this effect when I started using a CO2 monitor in my classroom as a proxy for air freshness during COVID. The CO2 levels in our supposedly "no problem with the air" classrooms shot up to 2000 ppm within minutes of the start of school and stayed there all day. Kids weren't checked out ONLY because I teach mathematics. They were breathing bad air, too.
Worse, when I brought the monitor home, I found the levels there were elevated even with no one home and surpassed 2000 with just two or three of us in a room.
The good news is that I stopped worrying about making my house "tight" for the sake of energy efficiency. I keep some windows cracked all year and don't worry about how tight the door seals are.
> The good news is that I stopped worrying about making my house "tight" for the sake of energy efficiency. I keep some windows cracked all year and don't worry about how tight the door seals are.
The point of having "tight" houses is not (just) about energy efficiency but about air quality as well. The general mantra is build tight, ventilate right. It's why modern building codes mandate air tightness and having ERV/HRVs.
By having a leaking house you do lose efficiency because in summer the air you paid to cool goes out and the hot-humid comes in, and in winter the air you paid to heat escapes and the cold comes in. But in addition to temperature (and humidity/moisture) you also get things like pollen, brake dust, (depending on your region) wildfire smoke, etc.
By ventilating right with ERV/HRV, you remove stale air and bring in tempered fresh outside air that you filter before distributing throughout the building. Air quality is also why 'spot ventilation' is also generally mandated at certain locations like over a cooktop/range in the kitchen, and in bathrooms (where the primary purpose is not taking care of smells (though helpful), but rather moisture from showers/baths).
> I would not want to live in a city where I have to be careful letting in outside air or going outside because there's too much air pollution...
1. Not living in a city (polluted or otherwise) still does not solve the problem of letting out cooled air and letting in hot-humid air in the summer, and letting out warmed air and letting in cold air in the winter. If your CO2 is high are you going to crack open a window when it's -10 outside? Or in the middle of a heat wave (esp. if you have AC and paid to run it to cool your house).
2. Not-city living also has pollen and other allergen leakage. You're also more likely to get wild fire particulates in less urban areas.
Building tight and ventilating right is applicable in all locations and all climates.
And in the extreme case, if you believe the outside is the healthiest environment, live in a tent or under a tarp. :) Buildings were invented to have a separate outside and inside, and leaky houses reduce the effectiveness of that separation.
Even if you live in an air quality paradise, it’s not ideal for your indoor air to be the air that manages to sneak through all the little cracks in your structure. Especially if you have cold outdoor temperatures, indoor humidity such that the outdoor temperatures are below the indoor dew point, and airflow through the walls that can lead to condensation and possibly mold in those walls.
Your indoor air should enter through windows or intentional intakes, not incidental gaps.
> Even if you live in an air quality paradise, it’s not ideal for your indoor air to be the air that manages to sneak through all the little cracks in your structure.
Small cracks are also things that critters may be able to get through.
Living in the countryside won't save you. I spent my childhood in a rural area and our house had the misfortune of being situated on a steep hill, so at all hours of the day and night you'd have cars and motorcycles and tractor trailers revving their engine to get up that hill. Every year we'd have to powerwash that road-facing side of the house to clean off the accumulated black grime, and sleeping with my window open, which faced that same road, always caused me to wake up raspy and hacking. Cars are a problem no matter where you live.
How much does implementing all that cost? What degree of benefit does it offer over simple window in situations where those concerns are negligible? What other benefits to human life could be procured with that money?
It just boggles the mind that people feel emboldened to only look at one side of the equation.
> How much does implementing all that cost? What degree of benefit does it offer over simple window in situations where those concerns are negligible? What other benefits to human life could be procured with that money?
Everywhere not being LA is actually an argument for ERVs/HRVs. The weather in LA (AIUI) is fairly even and consistent and it is probably fairly easy to just open a window.
But if you're in Texas with high humidity, or Arizona with high heat, or north of the Mason-Dixon line where people get winter, it's kind of hard to open a window when it's 0 or -10 outside. If you have stale air (perhaps as measured by high CO2) what are you supposed to do?
Over the July 4, 2026, weekend it's supposed to get >90F/>32C on the east coast of the US: do you want to open your windows and let all of that heat in? Especially if you already have an AC unit so paid to run it get your home's inside temperature down?
If you have a place with ducts, you can purchase an ERV and tap into that for US$ 1000:
And even in milder climates (like LA), have the ERV suck in air from the outside through an MERV 13(+) carbon filter, and not only do you deal with things like wild fire smoke, but wild fire smell:
>The good news is that I stopped worrying about making my house "tight" for the sake of energy efficiency. I keep some windows cracked all year and don't worry about how tight the door seals are.
You could also install an energy recovery ventilation (ERV) system.
I’m not saying this isn’t a legitimate concern but this really seems to have exploded amongst the tech community as the next obsession.
I see this pop up on X every few weeks. Is the concern about this really based on actual science? Is there empirical data proving people are less productive or are damaging themselves as a result of heightened CO2 levels? And I don’t mean observational epidemiology studies.
Anecdotal, but I'm convinced it screws up sleep quality. I'd just accepted for the longest time that waking up groggy with a slight headache and tired was the norm until I put a CO2 monitor in my room. With the door closed, it climbed up to 1500ppm in under an hour.
I'm certain many people are sleeping in similar conditions without realising and ventilating their rooms properly or leaving the door open.
> Anecdotal, but I'm convinced it screws up sleep quality.
It absolutely does.
>I'd just accepted for the longest time that waking up groggy with a slight headache and tired was the norm until I put a CO2 monitor in my room. With the door closed, it climbed up to 1500ppm in under an hour.
Same experience here. Opening windows just a bit totally changed my sleep quality.
IMO it's something where an intervention is often cheap enough that it's worth it even without great evidence.
But also bear in mind that regardless of "are we operating at max effectiveness", OSHA sets a legal limit of 5000ppm in a workplace, and that's about _safety_.
This article is talking about keeping levels below 1000 which is a very high standard IMO (still arguably justified given the studies mentioned). But if you are in a poorly ventilated home office you could easily hit 3000. At that point you are closer to "illegal in the US" than "earth's atmosphere".
So yeah even if you are unconvinced about micro-optimising your CO2 levels there's a very long established argument in favour of at least paying _some_ attention to it.
It's not even that hard to optimise at home. I've found simply leaving the door open to the rest of the house causes the room CO2 to not elevate much over baseline outdoor readings. Or just opening a window just a crack will rapidly remove all excess co2.
The real problem is offices and meeting rooms where you have 10 people in a small box for hours and windows that don't open.
Any affect from CO2 specifically seems weak. Clean air in broadly good though, and high CO2 is a good proxy for stale air. So I’m always supportive of people caring and paying attention to their air.
Along the way they’ll either learn about or accidentally mitigate other ills like radon, nitrous oxide from stoves, diesel particulate’s impact on test scores, etc.
We assume sometimes that everybody experiences this in the same way, but a lot of people might be super-sensitive to it, and others completely immune. It is quite possible that the ones obsessing about it are the sensitive ones, because they feel it much more.
I agree it seems like a concern fad. I talked about it once with my brilliant MIT-educated 20 year Navy submariner brother-in-law and he didn't commit one way or the other but did say submarines have CO2 in the low thousands.
You'd think (hope) if there was a big effect here on performance, the relatively cheap/easy solution of maintaining lower CO2 would be standard. I know people think of the military as dumb grunts who you don't want to think, but he was one of the four department chiefs onboard (Weapons, Nav, I forget the others) and they have pretty substantial responsibility to make decisions on their own.
It's peak HN meme material because 1) it (allegedly) affects your intelligence which everyone here values highly 2) you can measure it, it's a number 3) requires tech to measure it
So perfect for HN, you can obsess over numbers and tech and how to measure it endlessly and overhype the significance to trick yourself into thinking you're doing something useful.
You get to have your cake and eat it, no wonder everyone loves this topic.
(Also if you're a doomer type you can link this in with rising atmospheric co2 levels for extra points)
I've been designing my own ERV system for the house and have been weighing all the options, so I had this list in my head. Nothing dramatic, just the reality. We have allergies and like sleeping in a cooler bedroom.
Nope. Opening windows is very often disallowed - whether socially, or you'd need a hammer, or the space doesn't have windows. Or opening windows would have other downsides - letting in rain, or too-hot/too-cold air, or pollution, or ...
Can't let those stupid workers open a window and ruin the efficacy of the precisely engineered hvac system that lets the building hit LEED Platinum or whatever
Yeah. But even when you can, how many bosses might forbid it - because there's already too many arguments over the thermostats, or it's kinda noisy outside, or HR warned 'em of lawsuits for doing that when the air pollution numbers are elevated, or whatever?
That is also my impression. CO2 build up provides a neat opportunity to carry around sensors, track something, display graphs and formulate quantifiable sets of rules. And also is a (more or less) interesting topic to discuss with others. Seems highly appealing to a large part of the crowd here. Personally, I only observed that some people are obsessed about having always one or more windows open but I never personally experienced any non-obvious problems with CO2 buildup. At some point the air is just smellably getting thick and then you just air out. Wouldn't need sensors for that.
I’ve lived in Australia and France and I’ve always attributed the taller size of Australians to the excellent state of their ventilation in buildings. Vents (and rooms themselves) are systematically bigger than in France, and if you live in a healthy environment, with meat, lots out outdoors during teen age, and correctly ventilated classrooms during their 20 best years, it makes no secret to me that they grew bigger.
Meanwhile in France we heat classrooms by stacking 35 kids in a confined space. It saves on heating, plus condensation that makes windows opaque helps pupils concentrate on the blackboard, as teachers said during my childhood.
> I’ve lived in Australia and France and I’ve always attributed the taller size of Australians to the excellent state of their ventilation in buildings. Vents (and rooms themselves) are systematically bigger than in France
The average male height in France is 178.60 cm, while in Australia it is 178.77 cm:
France is indeed ridiculously bad at ventilation (not to mention air conditioning). Restaurants, offices, even gyms - most have bad to non-existing ventilation. Coming from the States this is just insanity.
In Quebec province in Canada, they added CO2 sensors in all the classes in all the schools after covid. Now what? Having data does not change anything if nothing is done.
If instead all the millions invested would have gone into adding air exchangers, now that would actually do something.
And that is assuming that CO2 levels really have an impact. From the last time I researched the subject, I found that there were few studies showing an impact.
For context, from what I remember, in submarines the CO2 levels are usually between 10 000 ppm and 20 000 ppm. Very far from 1000 or 2000 ppm.
Also, CO2 sensors are usually pretty bad. I work in HVAC and I hate calibrating them, the readings are not very consistent. Leave them alone for a few years and a good percentage will simply output bad readings.
Then you see things like a teacher leaving the windows open in winter because the sensor says 2000 ppm all the time instead of realizing the problem is the sensor. (CO2 levels should go back to atmospheric levels over the weekend for example at about 450 ppm)
I got one because old apartment and bad ventilation. Was able to open a window when I felt the effect before, but now I can get an alert earlier. Since getting it I could consistently feel the effect at around 11100-1300.
I'm in the indoor air quality business. This is real.
A good way to think about CO2 is as a proxy for dirty air. CO2 is easy to measure but what it really means:
The next breath you take has:
- already been inhaled and exhaled by others several times.
- contains remnants of their farts, burps, off-gasing from everything they are wearing, have, everything in the room, etc.
- may have presence of other gases like radon in the winter, mold spores, g-d knows whatever else.
- co2 itself has negative effects but mainly it's a signal of what else is probabilistically in your air, poor ventilation.
Florence nightingale the inventor of modern nursing wrote that making indoor air as close as possible to outdoor air (without freezing the patient) is the best and most overlooked input to wellness. I believe this is still true.
Weirdly there are people who for some reason are hell bent on denying the air quality as an input to health and cognition. The simplest way to reason about it is: the argument for organic food is the less toxin-like stuff in it the better. Same for filtered or spring water. We often fail to quantity the impact exactly but we (logically) know that less toxin is better. For some reason we hold a much higher bar for "blaming the air" which doesn't make sense.
By volume we consume exponentially more air than food or water, and it enters the blood stream faster and more directly so obviously it impacts us. The EPA ranks indoor air quality as a top risk.
Ironically we are obsessed with outdoor air quality and if you have allergies to things like pollen that's a real concern but in most cases outdoor air is the baseline for what's indoors + other shit is added.
I find that there are people who say "wow air quality here is bad" and there are people who say "oh man I'm tired lately" without being able to attribute it, but I don't ever see anyone thriving in what is objectively bad air.
Sorry forgot the thing most directly related to the article. Harvard did a study on air and cognition (Google Harvard cogfx) - here's the Gemini summary which tracks with my research:
Study 1 (Simulated Office): Participants in optimized "Green" and "Green+" office environments scored 61% and 101% higher, respectively, on cognitive function tests compared to conventional office environments.
Study 2 (Buildingomics): In a real-world analysis, occupants of high-performing, green-certified buildings had 26% higher cognitive scores and slept better than those in high-performing but uncertified buildings.
Home/Work Study: Researchers tracking remote workers found that suboptimal indoor temperatures and elevated CO₂ (indicating poor ventilation) directly harmed creative problem-solving and cognitive processing.
A major confounding factor is everything else in the air. Humans produce lots of different gases, and CO2 is usually a proxy for the overall concentration of our effluent gases. But in a submarine, or in some buildings, there are gas filters (usually carbon, possibly with various modifications) that can remove or destroy some of these gases but have no effect on CO2. So the air in a submarine at 15000ppm CO2 could be very different from the air in a an unventilated room that reaches 15000ppm CO2.
The first person to deal with this may have been Cornelis Drebbel in 1610 when he deployed the first submarine. With 4 oarsmen submerged in a leaky wooden sub, they’d have too much co2 and too little oxygen. Somehow they were able to stay for hours at a time.
Robert Boyle describes Drebbel’s use of a “chymical liquor” to refresh the air.
“Paracelſus, indeed, tells us, that "as the ſtomach concocts the aliment, "and makes part of it uſeful to the body, rejecting the other; ſo the "lungs conſume part of the air, and reject the reſt." Whence, according to him, we may ſuppoſe a little vital quinteſſence in the air, which ſerves to refresh and reſtore our vital ſpirits; for which purpoſe, the groſſer, and far greater part of the air, being unſerviceable, it is not ſtrange that an animal ſhould inceſſantly require fresh air. This opinion, indeed, is not abſurd; but it requires to be explain'd and prov'd: beſides, ſome objections may be made to it, from what has been already argued againſt the transmutation of air, into vital ſpirits. Nor is it probable, that the bare want of the generation of the uſual quantity of vital ſpirits, for leſs than one minute, ſhould be able to kill a lively animal, without the help of any external violence. And, upon this ſuppoſition, Cornelius Drebell, is affirm'd, by many credible perſons, to have contrived a veſſel to be row'd under water: for Drebell conceiv'd, that it is not the whole body of the air, but a certain ſpirituous part of it, that fits it for reſpiration; which being ſpent, the remaining groſſer body of the air, is unable to cheriſh the vital flame reſiding in the heart. So that, beſides the mechanical contrivance of his boat, he had a chymical liquor, which, by unſtopping the veſſel wherein it was contain'd, the fumes of it would ſpeedily reſtore to the air, foul'd by reſpiration, ſuch a proportion of vital parts, as would make it again fit for that office; and having made it my buſineſs to learn this ſtrange liquor, his relations conſtantly affirm'd, that Drebell would never diſcloſe it, but to one perſon, who himſelf told me what it was.“
I don't think you can cleanly compare this: In the study, they added CO2 to the room, while keeping O2 at normoxic levels throughout the experiment. In your meeting room, O2 levels will be dropping in lock-step with the CO2-levels rising. It may be the lack of oxygen that leads to drowsiness, not the additional CO2. But it's the CO2 levels that you can measure as a good proxy of overall air quality.
I don't think this is correct. The concentration of CO2 in air is about 0.04%, whereas the concentration of oxygen is 20%, so the partial pressure of oxygen is about 500x higher. This means that if, for example, 10% of the oxygen in a room spontaneously disappeared, it would be replaced about sqrt(500) = 22x faster through leaks in the room than a 10% spontaneous CO2 increase would dissipate. (This ignores a small effect due to the different density of the two gases).
So in practice the oxygen level can never drift meaningfully far from the atmospheric pressure, whereas carbon dioxide easily can because the pressures involved are so low.
Ok, fair points, including the sister comment, it's likely not a drop in O2 levels.
But then why can we see problems with concentration in studies of people in poorly ventilated rooms, but not replicate that when just adding CO2 to normal air? What is the CO2 that we can measure in meeting rooms actually a proxy for?
The Satish 2012 study that seems to have started this trend was a small cohort of 22 people split in 6 smaller groups where they also just injected pure CO2 in a small room. There have been several attempts to reproduce, which sometimes found no clear effect, or a significantly smaller effect.
This original study has been used to market these CO2 monitors for years, but the evidence is quite thin and doesn't support a strong effect. It seems likely that there is a small effect, and it has been wildly exaggerated thanks to a small study with N=22.
Can it not just be that what happens in stuffy meeting rooms is boring? Opening the windows changes the temperature, the noise levels, perhaps the light levels ≈ adds some novelty, which makes you feel a bit more awake.
I mean that can't be right, as the body's breathing response is triggered by that amount of CO2 buildup. It's not about what's in the air. It's about what the body can take up. Maybe submariners are self-selected to be more physically fit, e.g. larger heart, lung capacity etc. to compensate.
Though that study included a 45 minute acclimation period. Appropriate for submarines, but I wonder what the results would be in the first 1 / 5 / 10 minutes.
... which is entirely unsurprising given that exhaled air is about 50.000 ppm CO2 and can vary by several 10.000s depending on depth and rate of breathing. I actually consider the recent wave of findings that CO2 levels as low as 500-1000 ppm measurably affect cognitive performance and well-being to be a great example of how you can prove literally anything with statistics and a sufficiently small sample size.
One key difference is that submariners are rigorously trained to operate effectively in less-than-ideal environmental conditions, whereas Bob from accounting probably is not.
Two tips: if you want a stationary CO2 meter in a room, you can make one very cheap with a SenseAir S88 sensor (22 Euro) and hooking it up to an ESP board. Flash ESPHome and you can get live statistics in your Home Assistant dashboard. The S88 is a pretty good optical NDIR Sensor that auto-calibrates by putting it in the outside air or in a well-ventilated room every N-days (N is in the data sheet). A bit more info about hooking up the S88:
If you want something with a display that works on batteries without spending over 200 Euro for an AraNet, the SwitchBot Meter Pro CO2 is pretty good option. It is regularly on offer below 50 Euro. It uses photoacoustic NDIR, but does not deviate a lot from the S88. You can use it without a SwitchBot by configuring it with a phone on Bluetooth. The meter works on external power and battery, but even when on battery, you can set the reporting interval to 5 minutes, which is good enough in practice. The meter broadcasts the measurements with Bluetooth LE, so if you want to get the data in Home Assistant, you can place a ESPHome Bluetooth LE Proxy in the vicinity [1]. This is an ESP32 flashed with ESPHome that listens on Bluetooth LE advertisement and forwards them to your HA instance over WiFi. Of course, you could also get the SwitchBot Hub, but what is the fun in doing that? :)
I would avoid the Ikea ALPSTUGA, it uses a thermal conductivity sensor, which is a very indirect method for measurements and it's often several hundred ppm off.
I would recommend Ruuvi Air, its sensors are high quality, and is quite open for devs to do pretty much whatever with it. Works by broadcasting sensor data over BLE, so if you have a smartphone or a home assistant server with BT connectivity, you can display or store the data live. The iOS app sends alerts when different custom thresholds are crossed, like for co2 ppm.
They do have a gateway product, but it’s not necessary if you have HA. If Apple homekit routers supported BLE as source it would work seamlessly in the ecosystem, but a bridge software is required on HA.
Looks like it's increased in price unfortunately but I like the idea, it's basically just what you would do as a DIY project but ready built. So you can either use it like a normal commercial product, or you can just fork the ESPHome config that's on GitHub and flash it exactly like any normal ESPHome project.
Thanks for mentioning that, last week I got 2 SwitchBot hub mini, 3 temperature sensors each, for 70€ total, they are really neat. Even put one in our fridge, I didn’t expect the signal to pass but it’s working :)
Will look at adding the CO2 monitoring
Edit: actually, they only sell them as part of a 6-in-1 device, with a display, and a bunch of other sensors. That feels overkill, I wish they would just sell the CO2 sensor itself
This reads to me as AI generated. Apparently it's still good enough to the general audience to be the #1 post on HN right now though. Which is honestly a troubling signal for the state of the world...
Nice! Have you considered doing a Show HN for that?
That's valuable in at least three different ways: public education, showing that most of the articles are still human-written which can be easy to forget about sometimes, and as an easy way to cross-validate my intuition when flagging something as AI-generated without having to manually run Pangram.
I despair a little bit about how many HN voters either seem to want to read slop or don't understand when they're reading it. This post is obviously AI generated from the first paragraph on, and still has 480 votes.
I bought a $30 CO2 monitor a couple months ago, and it confirmed my suspicion that my home office (a normal room about 12' x 18') reaches unhealthy levels over 1000ppm after just a few hours; opening a window quickly restores levels to the 400-700ppm range.
Afternoon mental fatigue solved. Highly recommended.
Fantastic, did you go for a particular "trusted" brand or just went on vibes? How should one rationally approach shopping for a CO2 monitor for home office use?
Oh this is absolutely so relevant and I wonder if there are any high quality studies that have analyzed driving performance against CO2 buildup in cars. Cars often ship with circulate air feature in the aircon, and people use it aggressively, nonchalantly at least where I live, having no idea about the dangers of possible hypoxia and sleepiness that might be inducing in them while driving. It is absolutely critical in my opinion for cars to have CO2 monitors. We put so many sensors in cars these days that this seems to be a really cheap and fairly high value of life addition that could possibly prevent accidents on roads. I keep a portable CO2 sensor in my car at all times, because sometimes circulation is not something I can avoid when stuck in traffic or when passing by a drain.
Got a firsthand experience with this. I was dropping off my girlfriend and we stopped to talk in the car, with all the windows up. Over the course of the conversation we got more and more agitated at each other until I had a thought and pulled my Aranet out from my backpack. It was >3000ppm CO2. We opened windows and within 2 minutes all the agitation went away.
To be fair, that might not just have been the CO2 dropping, but also the pattern interrupt + giving you both an easy and face-saving way out of that situation.
I'm not sure this is a helpful comment. This is a common story with many medications, where someone notices their feelings are off and suddenly remembers that there is a probable root cause. It's why medications list side effects.
Your comment actually has me convinced that this isn't an issue. I've been a recirculation dude for my entire life, I literally don't drive any other way.
Yeah, I measured over 5000ppm in a taxi with two passengers. Showed the driver how to enable air intake (he didn’t know about the feature) and tried to explain this is deadly. Pretty sure this is commonplace globally.
Generally it’s a miracle to me so many people survive traffic on public roads, statistically.
Don't forget too, if the CO2 is 1000 ppm, then half of the air in each breath you inhale was recently exhaled by someone else. Yes, airborne viruses are still spreading. I still wear an N95 mask whenever I'm in an indoor space with other people outside of home.
IKEA now has a remarkably cheap ($35) air quality monitor that measures CO2 as well as PM:
I don't have one yet but plan to pick one up soon. A CO2 sensor alone from Adafruit is $50+, though that one is more precise. I bought it a while ago and it's still sitting in my todo bin.
I haven't heard that 30 minute figure before, you have a reference? I've seen articles about medical workers using masks for much longer.
Installing air filtration and UVC in classrooms and meeting rooms certainly helps.
Since the mask shortage cleared up, HCW have been advised to stop re-using them. I re-use mind til they get dirty, but maybe I should replace them more often.
I've noticed that cooking with gas is easily the worst thing for CO2 levels. Even with lots of ventilation my kitchen will hover around 1200ppm until it's over with.
I swear I can feel the 430ppm already. I was born into a world with 340ppm. I can't imagine what it's going to be like when we hit 500+ globally.
I'm in the market for an active CO2 scrubbing solution that I could deploy at home. Scrubbing the entire planet won't work but I could make a small room feel like 1960 again.
Controlling indoor CO2 is important, but it's a proxy metric for the escalation in indoor bioeffluent VOCs which are a tiring subset of total VOCs. This is why scrubbing indoor CO2 will by itself never produce the pro-cognitive result you want. See https://www.aivc.org/resource/effects-carbon-dioxide-and-wit...
Also, when you cook on a gas stove, it produces numerous other toxic gases which too are critical to ventilate before they even escalate, failing which the lung cancer is risked.
Scrubbing indoor CO2 is sensible only when you want to go below the outdoor CO2 level, not at levels above it.
I do feel impaired around 1000ppm. I get headaches. At home I got a few Air Gradient Ones (no affiliation, but they are great) and connected those to my Home Assistant to turn up the ventilation in stages (above 650ppm go up, above 800ppm again, at 1000ppm max). I also do this for the bedrooms, cause in the night it goes up too.
The article talks about "within the hour". With four people in my living room doing normal things it jumps within 20min to around 1000ppm. If I am wrestling with my kids much sooner.
In offices companies often neglect it.
edit: if you are cooking on gas it also has an immediate effect on co2 of course apart from other small particles
This article is rated 100% on my AI smell meter, making it less trustworthy despite convincing arguments.
For instance, I'm now really only sure that author measured a 2000 ppm CO2 in a meeting room once. Everything else could just be LLM trying to invent convincing argument.
Not gonna happen in Germany. I don’t think I‘ve ever seen a windowless room here and it’s common to open all windows at once for a few minutes, just to replace as much air as possible:
Take a look at indoorco2map.com and you will find plenty of places in Germany with bad air measured in a crowd data collection effort. Most notably doctor‘s offices are often very bad. Many supermarkets too. Schools are not well measurable this way but academic research shows they often are at 2000-3000 ppm or even higher. (Disclaimer: I built the website/App)
I noticed this effect really strongly at university. There was one particular lecture hall that was effectively buried in the side of a hill; I can't count how many times I had an early afternoon lecture in there (so it had been in use since 8am), where I just could not focus or stay awake. Assuming sleep deprivation was the problem, afterwards I'd head out and lie down on a bench to take a nap, only to find myself wide awake. I have no trouble taking cat-naps when I'm actually tired, leading me to eventually conclude it was CO2 / O2 in the room that was the culprit.
If your CO2 levels are that high then you should fix the HVAC system and get it up to code or lobby for fixing the code. In many countries, a full air exchange in any office space every X hours is mandatory. In other countries that's optional and they need to get their act together.
CO2 is just a tip as office or home is toxic environment anyway. Plastic (e.g. carpets), formaldehyde in furniture, air fresheners… add home office and cooking at home (-> small carcinogenic particles)…
If you start reading How not to die by Michael Greger, you find out that dust, soda and sitting - not CO2 - are real killers…
It's similar to how people think sharks and airplanes are the biggest killers - when in reality it is coconuts, mosquitoes, and motorcycles.
Air filters, decluttering, regular deep cleaning, replacing dust-friendly surfaces and furniture (such as carpet, drapes, and upholstered sofas) with things like wood, vinyl, or leather. HVAC maintenance, cleaning, and filters. Washable allergen covers for things like pillows and mattresses.
HEPA-filter air purifier and a robot vacuum that is scheduled to run while your are not in the apartment (to reduce baseline dust) are probably the most simple/cost-effective measures.
Air purifier is good for PM2.5 and other microscopic pollutants but it doesn’t do that much for dust unless it’s particularly light dust and very close to the purifier.
Dust is much more likely to just settle on the ground and be kicked back up than it is to move all the way to the purifier to get stuck in the filter.
I have an air purifier with built in particulate sensor. It doesn't provide numbers, but has a multi-color LED indicator to report PM2.5 level as good/mediocre/bad/terrible. Running a vacuum cleaner that supposedly has a good filter consistently increases the reported PM2.5 level from the first band to the second. The air purifier (or faster/cheaper depending on the weather, just open some windows) can bring it back down again.
Can someone provide an explanation why CO2 concentrations above 1000 ppm have such a negative influence given the fact that CO2 concentration in lungs (at rest) never falls below 10000 ppm?
Per Wikipedia, at rest 500 ml of inhaled air is diluted with ≥2500 ml [1] of residual air in lungs containing ≥40000 ppm (4%) of CO2 [2]. Other things being equal, increasing concentration of CO2 in ambient air 10x (500ppm -> 5000 ppm) would increase concentration of CO2 in the lungs after taking the breath by less than 2.5% [3].
I imagine it could easily be compensated by an equivalently minor increase of breathing rate or breathing depth.
> Then, somewhere in the second hour, the room quietly gets worse at making them.
Maybe it's not just the air but also the multi-hour meetings that drive people to a sense of "oh god let this finally end now", which leads do decisions that fall short.
A reasonably popular brand's product that uses an NDIR sensor revealed to me just how much the CO2 level increases each night in my two bedrooms.
One of them seems to have much worse ventilation to the extent that it reaches double the level. Opening the window slightly 24/7 keeps it low.
My fiance's chronic headaches/migraines/idk became noticeably less frequent after this change and when they do occur it's usually because the window was accidentally left closed.
Anybody who struggles with this kind of thing might want to try checking their levels. Or just open a window I guess?
Does it work the other way around? Does breathing air with 0% CO2 improve human cognitive performance? I haven't been able to find any research on the effects of lower CO2 concentrations.
At a career fair in an auditorium I was showing a sensor suite with OLED displaying current readings, one of which was the SCD41 CO2 sensor (they cost more than the esp32!)
I watched the sensor rise from 800 to 1700 PPM by the time the last group left the
It’s quite easy to build one and deploy with esphome and breadboard with stuff you can order on Amazon and have an LLM walk your through hardware and setup.
It is interesting where the rate of speech quickens as the co2 rises and the body starts to notice the co2, or maybe that was just the coffee.
A bit OT, but was anyone else amazed by the bad UX of that CO2 monitor in the picture?
If you notice, that monitor has a "traffic light" gauge at the bottom to tell you if the current CO2 level is critical. That traffic light is currently showing RED, i.e. highly critical.
The thing is essentially sounding the alarm and prompting immediate action. However, became the traffic light colors are printed on and static and the only dynamic indicator is a small e-paper bit above the color gauge, the effect gets lost completely.
These CO2 monitors have a configurable audio alarm. The present model uses an e-ink display to conserve battery. Physical LEDs would also work, but really in practice you don’t look at the unit and instead are notified by the audio alarm.
For the DIYers, it's simple to get an SCD4x sensor and hook it to a pi, arduino, ESP32 etc (then use CC to create a live web interface). I did this after trying an Inkbird CO2 monitor, which gets reasonable scores in reviews and wanting a live web report in the office.
Interestingly the Inkbird and the SCD4X quite often diverge by anything up to hundreds of PPMs; I kind of back the SCD4x (on a Pi in my case) for accuracy after lots of experimentation, reading the datasheet and ensuring the correct calibration procedurs are followed (basically expose the sensors to outside air once a week).
It's also interesting how much it varies day to day in my one-person office - possibly down to how windy it is outside, even with windows closed one day it never goes about 800ppm, other days it'll hit 1500ppm by lunchtime if I don't open a window.
N.B. Quite possible the Inkbird uses an SCD4x internally, seems reasonable kit so I have no explanation for the differences in readings.
Get a sensor with NDIR system and it should be good. I myself have felt cognitive functions decline during my remote work sessions at home. I have smaller room that gets filled with CO2 when my family visit the room.
Comprehensive AIR monitor system is must to get most efficient output. Author is right here!
i literally had a co2 sensor for my engineering team last fall cause the space was so poorly ventilated. just measuring it continuously radically changed how everyone approached using the space packing wise and ventilation. smelled better too :p
I tend to agree with this observation. I started taking my evening calls (6:30 to 10:30 PM everyday) from my terrace in open air and my overall fatigue became quite less and I feel quite less tired compared to earlier time when I used to take these calls from my room.
I remember some years ago after coming from work at 6 pm I was dead tired at home thinking it was due to hard work during the day. Then one summer day decided to code side projects on my balcony and I was building until midnight full of energy.
Goes a long way to prove that industrial air conditioning is absolutely abysmal. If air conditioning actually worked satisfactorily, opening a window should never be necessary unless you want the cold waft of air, while the air conditioning actually delivered high-quality, low-CO2 air without smell.
Instead any room at > 20% capacity is quickly filled with CO2 and the putrid smell of bad mouth and body odour.
I get it that perfect ventilation would be way more expensive, but at the current level it is just bad, and the windows are sealed shut. It does not make sense from a human perspective.
Working from home next to my open window feels generally way better then being in the office. Perhaps this is contributing. Still, seems more of a case for WFH rather than against, as article mentions some people have tried to make the case for.
I have a CO2 monitor and I don't understand one thing - it seems that CO2 increases more quickly during summer than during winter. If I close my windows it takes longer to reach 1000 ppm during winter than it does during the summer.
I didn't gather concrete data on this but this is just what I eyeballed over the last few years. Does anyone know why could this be the case?
I find it kind of funny that we've been low-key suffocating the higher order function of our brains ever since we started building structures to live in with very little awareness of it. My mom is one of those people who complains that the air is getting stale and opens a window, the hero we needed.
Not that we need more anecdotal evidence but I’ve long felt a certain restlessness and inability to think creatively somewhere in the early afternoon. I work from home with my wife. I’ve eliminated lunch, coffee, and a ton of other variables. The one variable that finally had a distinct effect to my mental state was opening a window.
I wonder if the corona times trend to WFH and jump to Teams/Zoom/etc meetings instead of physical meetings had/has a positive effect in regards to this.
I also use my Aranet everywhere. The nice thing is you quickly develop a feel for when you need to ventilate spaces you know so you don’t need it there anymore. I also developed a feeling for new (to me) rooms a bit.
I once woke up with the fam in a hotel with airco at 5500 ppm. It is then that I learned the airco does not blow fresh air (logical after thinking about it).
My employer started using CO2 monitors in meeting rooms 15 years ago, it’s really a useful thing to have. As well as the meeting rooms having windows you can open.
One easy way to fix this for many people's bedrooms or home offices: look at your HVAC system, and there's probably an option to have the fan run all the time, even if the heat or air isn't running. Turn that on, and your home's CO2 levels will drop substantially.
The practical bottleneck for most AI tooling isn't model capability anymore - it's the orchestration layer. Getting reliable behavior across edge cases requires more engineering than people expect from demos.
The really uncomfortable part is that 1000 ppm isn’t that far off from how EARTH will be. A terrifying scenario that will be like Total Recall with people clamoring for and paying for fresh air. Those that can’t will be permanently in a stupor.
The building science community has not buy and large came to the agreement that the CO2 itself is the cause of the cognitive decline. It could be the Canary in the coal mine telling us there is an accumulation of compounds causing the decline.
Why that matters? You need good ventilation regardless, but instead of just thinking of CO2, try to minimize compounds in your air by selecting things for the room that smell less and off-gas less.
Similar to this a closed motorcycle helmet without air circulation increases CO2 extremely rapidly, within 60s it's already at really high levels. Open your visor when you stop!
open a window, wait, ok, ok, turn up the , wait, no, ummm, hmmmmm
re, re, no forget that, hmmm
anyway, as a person with a strong interest in civil engineering, systems, and the subset of air handling, I can say that there has long been disenting arguments about how things are built,that have been ignored due to cost, which are large in terms of internal volumes required, and the intractable issues around, noise, filtration, heating/cooling and maintenance.
And as the climate warms, and in many areas pollution increases , the inadequate methods used to "calculate" requirements, get further from real world needs.
You could try throwing a desk through a window, but as that is one of the things the planners and engineers have antisipated, it will prove to be surprisingly difficult.
Make them mostly async, bringly only the very pointy details that need nutting down sync. If knowledge transfer is needed in a meeting that could be done seperately.
Put it this way do you need to book a 3h meeting with your spouse to decide if to buy a house? Nope all the research and decision criteria were in advance. That final minute of making the decision is a cross check over that work.
I really wish a Apple or another major OEM would integrate CO2 monitor into watches or smartphones. Suddenly, everybody would be aware of the CO2 level in the room, get alerts, etc. and the problem will just solve itself.
There are so many rooms, classrooms, movie theaters and other places with poor ventilation where you just feel dizzy, or fall asleep, not knowing it was just due to lower oxygen levels in your blood. Raising awareness is the only real solution.
> I really wish a Apple or another major OEM would integrate CO2 monitor into watches or smartphones
CO2 levels are locally elevated in the area where you exhale. Someone sitting at a desk with their hands on a keyboard exhaling through their nose would be producing a directed stream of elevated CO2 straight at the sensor on their wrist. Same thing if someone puts their phone on their desk.
Even with the IKEA and other cheap sensors that are becoming popular, there is a learning curve where users discover that putting it on their desk right in front of where they’re breathing produces higher numbers than having it even 5 feet away.
The false positives from having a CO2 sensor that close to everyone’s face would be causing unnecessary alarm all over.
> There are so many rooms, classrooms, movie theaters and other places with poor ventilation where you just feel dizzy, or fall asleep, not knowing it was just due to lower oxygen levels in your blood. Raising awareness is the only real solution.
If someone is falling asleep in this many different places I would suspect undiagnosed sleep apnea or another condition first and foremost. Spaces like movie theaters have very high volumes of air due to their size and commercial building HVAC has much higher standards for air circulation than even your home. If someone was falling asleep in so many different places then the most likely common theme is that person and it should be checked out!
This is another reason why putting CO2 sensors on everyone’s wrists would be a mistake: It would start getting blamed for every vague condition people experience. This has already happened with wrist-worn heart rate monitors. My friends in the medical field see people all the time who come in with vague complaints and they’ve self diagnosed as being related to their heart because they can see their heart rate now.
You also have the wrong idea about what elevated CO2 does. It doesn’t reduce the oxygen levels in your blood. It makes it more difficult for your body to expel CO2, which can produce subtle changes in many processes.
> CO2 levels are locally elevated in the area where you exhale.
That's the same area we inhale from... Wouldn't be right to measure there then? It's not like we're interested in the amount of CO2 on the ground (in this discussion)
No, because the studies that establish the levels correlated with cognitive changes use ambient CO2 levels. Not with a stream of air directed, maybe, from your nose to your wrist.
It is not possible to come up with a different baseline for wrist-worn monitors because the measurements could change significantly based on even small factors like the position of the wrist or smartphone.
The air infront of you IS the air you breed in, why shouldn’t it be measured?
Because the thresholds everyone gets from the studies were not measured in that location.
It would be like the weather station telling you it was 160 degrees outside because they put their thermal sensor on the asphalt, but you wanted to know the air temperature.
Or your watch telling you the room is 98 degrees because it's only ever measuring your body temperature
That’s a much better example. Thanks
> There are so many rooms, classrooms, movie theaters and other places with poor ventilation where you just feel dizzy, or fall asleep, not knowing it was just due to lower oxygen levels in your blood. Raising awareness is the only real solution.
Not wrong, but it is perhaps worth noting that there are already standards for proper ventilation. Generally you're looking at 5–10 cfm/person (2.5-5 L/s), depending on the facility and purpose of the room; see Table 6.2.2.1 in ASHRAE Standard 62.1 for the US:
* https://www.ashrae.org/file%20library/technical%20resources/...
Maybe set up a monitor, but if the room/facility has recently been renovated and meets modern (>2013) building codes, this 'should' have already been taken into account.
Should…
Whenever I travel, I bring a CO2 meter with me. It’s amazing how often the air is bad. Often in unexpected places. My meter hit 3100 in an uber once. I didn’t even notice until I got to my hotel room and looked at the data log. It was a fresh, hot day outside. The uber had windows closed and AC on. I bet he had no idea - but he was driving with significant cognitive impairment. Takeoff and landing in planes are always the worst. If you get sleepy as the plane is taking off, it’s not you. The plane’s ventilation doesn’t work properly when the plane is stationary. So before a plane is in the air, they often hit 2500.
When was the last time you had that sensor calibrated properly with a can of test gas and a multimeter?
Take it outside, as long as it measures 400-450 it's probably good.
Metrology calibration is necessary if you want accuracy better than 10%, but most of us don't care at all about that, instead we care about increments of 200ppm or more.
Haha yes. 400-450ppm is fine. We’re doing just fine here. Everything is okay.
https://www.co2levels.org/
The comment was about the accuracy of the sensor, not about raising CO2 levels across the globe.
Local factors can make your CO2 fluctuate by 200ppm. If you're near a busy road with not a lot of wind 600 ppm is possible. But it's not that important if you open your window at 1000 ppm or 1200 ppm.
Building codes that address this are wonderful, however:
- Plenty of people live or work in older buildings, where are not up to standard. For example: my office probably violates the air quality sensibilities of the Victorian era, which is when it was originally built.
- Equipment breaks down, isn't operated properly, or wasn't installed correctly. Having monitors that measure air quality is an extra check. While you may not be able to get direct action upon a consumer sensor, it can help you push for action.
I've been in buildings of varying quality over the years. I've seen how it takes time to get people in to do air quality testing. Heck, I saw the government claim that the air quality was acceptable in schools during the pandemic because the schools had passive ventilation systems. That meant they could open windows. (To be fair, the air quality in most of those buildings was probably fine since that was how the buildings were designed. That said, such standards make it easy for some buildings to slip through the cracks.)
So yeah, sensors to the people!
This is correct, but there's still a lot of opportunity to do better.
I've been involved with the build out of several office spaces in new and old buildings. We always took this sort of thing seriously and measured each room independently for a week (many at a time) ensuring we accounted for periods of high occupancy.
This let us tune the HVAC systems to operate more efficiently, ensuring comfortable temperatures and air circulation. Every time I've seen this done there were structural deficiencies that required remediation, some times it meant adjusting duct work.
Most modern office buildings are designed to be a platform for constructing spaces, as spaces usually evolve and change between leases and tenants. They're designed to accommodate this sort of thing.
However I've found that no build out nails this the first time. It's very hard! Often times things look fine but once you get people in the space things change drastically. It requires time and effort to address.
Several of my offices had such good air that I'd prefer being there over pretty much anywhere else -- even outside on poor AQI days.
I've also found that a lot of offices don't do any of this and their air quality is noticeably poor. And lastly I've found that the oldest buildings, including schools -- and I'm talking really old -- have very good air because they are so incredibly leaky. They're usually harder to cool and heat, though.
I think modern domestic houses its the opposite. At least in Netherlands insulation is such a strong focus, due to climate change I think, that modern appartments have terrible ventilation
Stayed at a beautiful new house in Finland, with five people instead of the usual two, the CO2 detector intermittently went off while we were sleeping. Which the hosts assured us was a faulty detector. They also spoke to how extremely energy efficient the house was, to us it seemed like there wasn't enough ventilation, to improve the insulation. Against their wishes, I slept with all windows fully cracked, which was only ~2 inches due to the "efficient" design.
This was probably CO not CO2? A CO2 monitor doesn't "go off", it just silently reports. CO would go off because it's deadly to have a CO leak.
> I think modern domestic houses its the opposite. At least in Netherlands insulation is such a strong focus, due to climate change I think, that modern appartments have terrible ventilation
The link I pointed to is all about ventilation, so just because people ignored an important component of building science, and focused on one aspect, does not invalidate it.
And while climate change is important and using efficiency to deal with it is useful, the thermal control layer is actually the least important of the four:
* https://buildingscience.com/documents/insights/bsi-001-the-p...
'Bulk' water (precipitation) and moisture can cause deterioration of the building materials (rot, crumbling), and also mold, which has its own health effects. Leaky houses can often blow conditioned air at much faster rates than thermal leakage.
How modern? We built or house in Belgium in 2016, and it was completely sealed, very well insulated, but the air quality was good because we had mechanical ventilation. Clean air blown in, stale air extracted which then went through a heat exchanger.
The only issue this house had was it overheated. We had glass facing south. Even in winter it instantly became too hot.
Heat recovery ventilation is the answer to this. You also get the benefit of being able to filter it.
Energy recovery ventilation is the answer to this.
HRVs only deal with temperature, but then you have humidity that is non-controlled: moisture coming in during the summer, and getting vented out in the winter (too-dry air coming in).
ERVs handle both.
A friend of mine recently moved to a modern apartment, built only a few years ago to a very high isolation standard (Germany). I stayed over night and slept on his couch, the air got really really dry and stuffy. It was really uncomfortable.
I think the issue is that the common tech requires sensors in an air-chamber. E.g. NDIR works by firing IR at a frequency that is absorbed by CO2. A sensor on the other side either measures the amount of IR light that got through (optical NDIR) or pressure/sound waves (photoacoustic NDIR). I guess that it's hard to use any existing sensors, because they are relatively large and probably water could easily get into the chamber.
Would be extremely cool if Apple, Samsung, and others can crack this, though I think they'd have done it already if it was easy.
Sensiron STCC4 uses thermal conductivity sensing thats very compact (4x4x1.2mm). It's pretty new to the market, but maybe in the future it'll happen.
Oxygen sensors used in car catalyst systems use a different effect based on electrochemistry. I see no reason that couldn't be minuaritized to grain-of-sand size.
The question is if oxygen levels are as good an indicator as CO2 levels... I suspect not.
Based on numbers, O2 concentration is probably not a good indicator.
Clean air contains about 20.9% O2 and 0.04% CO2. At 2000 ppm CO2, which according to the author is bad enough to impair judgement, that's 0.2% CO2, it that CO2 is the result of respiration, it means that about 0.2% O2 was consumed, so that's a drop from 20.9% to 20.7%, a very small difference. 20.7% is not low enough to have a significant effect, the CO2 itself is the problem, not the drop in O2. And using O2 concentration as a proxy for CO2 doesn't look reliable to me: the difference is small and other things, like humidity can affect O2 concentration.
As for the sensor, O2 sensor in cars compare the O2 concentration between the outside air and exhaust gases, it needs outside air as a reference, but what you are measuring is the outside air itself, you don't have that reference.
>that's 0.2% CO2, it that CO2 is the result of respiration, it means that about 0.2% O2 was consumed,
I dont know anything about human respiration, but I know a little about chemistry and theres no reason to assume this is true. Basic stoichiometry.
According to a random article on the internet[1], nominal co2 production is 80% of oxygen consumption.
Your point appears broadly correct, just wanted to point out some faulty reasoning that could lead to incorrect results in the future.
[1] https://societymechanicalventilation.org/wp-content/uploads/...
CO2 concentration doesn't start at zero, and by coincidence, if CO2 production is 80% of oxygen consumption, consuming 0.2% oxygen results in 0.16% CO2, add it to the base 0.04% and you get 0.2%.
> O2 sensor in cars compare the O2 concentration between the outside air and exhaust gases, it needs outside air as a reference
Source?
https://en.wikipedia.org/wiki/Oxygen_sensor#Automotive_appli...
It looks that some O2 sensors that don't require a reference have been used (titania sensors) but even though they have some advantages, they are less precise and mostly obsolete.
I had a project miniaturizing nasa tech for detecting hypoxia with o2 and CO2 sensors. It used a phosphorescent dye that changed a delay flash (ie you blinked a light, the dye would absorbed and blink back after a delay) based on temp and o2.
CO2 was measured with infrared but water also absorbed it, so you need to heat things up enough to not have water. It can be small, but not watch small.
All and all interesting stuff!
> CO2 was measured with infrared but water also absorbed it, so you need to heat things up enough to not have water. It can be small, but not watch small.
Can't you just measure CO2 "naively"; but then also, separately, measure rH; and then use the rH value to grab a research-calibrated LUT to pass the raw CO2 value through?
(I presume this is why all the little standalone CO2-sensor boxes you can buy also have rH displays. They're measuring it anyway to normalize the CO2 value, so they may as well make it a feature and display it.)
Electrochemical pile style oxygen sensors continuously deplete themselves whether actively measured or not. Common smart home oxygen piles have a fixed lifetime of a few years, and they're quite sizable (probably about as much volume as a whole smartwatch). Putting the same chemistry in an even smaller package would likely result in lifetime measured in hours
I assume this is because of diffusion of materials at elevated temperature. The sensor would, I think, require a lower temperature than an electrolyzer, since the current would be much lower. But it would be best if lower temperature solid oxide electrolytes could be discovered.
The ones in cars need to be heated up quite a bit in order to work, and you still need reference air. Otherwise, I'm pretty sure that CO2 isn't a problem but rather an indication of a lack of oxygen in the first place, so it technically could work... just not if you're measuring the environment itself.
This is in theory not a problem: getting an oxygen sensor to 700 degrees if it's a tiny spec on a chip is not necessarily hard or would even require a lot of power.
But...oxygen concentration is essentially indepedent of CO2. We measure CO2 at part per million levels, whereas O2 is 20% of the air.
(In that context CO2 is surprisingly toxic given that 1000 ppm can impair mental acuity).
> whereas O2 is 20% of the air.
The goal of a gasoline engine's sensor is to accurately and precisely measure the point where O2 concentration reaches zero, so ambient air levels are not quite as relevant.
No, it's nonsense to assert that CO2 is due to a lack of oxygen.
I don’t think we actually care about co2 levels. I think we use them as a proxy for o2 levels (same as our bodies do). So your idea would be great.
> I think we use them as a proxy for o2 levels (same as our bodies do).
Probably. ISTR that depriving a body of oxygen results in a different response than overloading the body on CO2. It's why if you completely displace all air in the room with CO2, people choke, panic, etc, but if you use Nitrogen, people just keel over dead without realising it.
The evolved response to CO2 is part of the human body’s ability to filter and remove CO2 via the respiratory system. AFAIK we don’t have similar capacity for Nitrogen because it’s not a primary waste product of that system.
Dissolving CO2 in water creates some carbonic acid (H2CO3) that will decompose back to water and CO2 when the CO2 concentration drops. Blood has a fair bit of water, and carbonic acid is much easier to detect than oxygen or nitrogen gas
We evolved to detect CO2 because that's by far the easiest thing to detect that's still a reasonable proxy for the performance of our respiratory system
I'm pretty sure that in a room where we replaced nitrogen with co2, we would be dead even if O2 concentrations were the same. Something about partial pressure. I notice AI explanations agree with me (not going to copy and paste them).
EDIT: ignore this; I was confused / misinformed
It's about pH. CO2 creates carbonic acid when it dissolves in water. Your blood pH, in turn, controls how much you feel like you need to breathe. So with high CO2, your respiration rate slows down, and that can lead to low oxygen levels.
Note that the physiology and biochemistry of this is complicated (e.g. blood is a very good pH buffer and it's actively regulated by kidneys etc) and it's very much a nascent field of research, so I think AI will be overconfident and hallucination-prone.
Source: I worked in high-co2 caves for my PhD so have read about this a lot. I always carried a CO2 monitor. Our rule was to get out if we saw 20,000 ppm or greater. I spent thousands of hours above 10,000ppm.
My medical student flatmates were talking a lot about acidosis and alcalosis :)
It was the first time that I heard about them. These basically never happen if your body and environment are halfway decent, but they are important in exceptional situations.
Wouldn't high CO2 make you breath faster?
Interesting, the linked article does say that.
Pretty sure I learned the effect was the opposite (high CO2 --> slower respiration). Note that that was ~15 years ago when I would have read that. Maybe I just misunderstood, or thinking has changed.
edit: reading now I see I was wrong about this. Thanks for the correction!
You are right about the pH implications, but respiratory acidosis leads to hyperventilation, not hypoventilation. CO2 will kill you regardless of oxygen supply.
https://en.wikipedia.org/wiki/Hypercapnia
This is extremely wrong: CO2 impairment kicks in around 1000 ppm[1] possibly lower.
You can hit this breathing by yourself in an unventilated 3x3m room (literally measured in my house).
1 https://pmc.ncbi.nlm.nih.gov/articles/PMC4892924/
You hit it even easier when driving in a car with the internal circulation turned on to keep nasty fumes out.
In a car with Recirculation Mode on Levels routinely spike between 1,500 and 4,000 ppm within 20 to 30 minutes.
I wonder how many driving accidents can be saved by having a co2 monitor in the car.
What makes you think that?
We do.
Huh. You don't know that, and are making it up. It's almost certainly false.
Mesh with the other Apple/et al devices in the room to take multiple samples and aggregate the results for an overall picture of the ambient co2
Just waiting for the followup post on HN: How I sent CO2 warnings to my entire office using an ESP32
What if a movie theater puts an Apple CO2 meter next to an air inlet? Everybody will think the air is safe.
If that’s the sole source and the application does thoughtful analysis it could determine that there are sections of the room that are better than others, yes
But realistically, using what sensors?
And (maybe less realistically) what if the theater puts 5 Apple sensors inside a sealed CO2-free chamber, spread around the room?
That’s the point of this thread that each device would have a small sensor that would sync and aggregate with others in the room
I think the thread established that CO2 sensors are too bulky for that.
So were most other sensors before Apple (and their suppliers) miniaturised the sensors. Gps and imu was huge in the 90s, several pound each.
I guess the problem is with the price of the sensors. Just look how expensive the Aranet 4 home shown in article is. There are worse devices for less like the IKEA alpstuga. I also don’t know how much electricity they pull.
I would hesitate to say the IKEA is worse. Inside the IKEA is a reputable Sensirion all in one sensor module. It's much cheaper and smaller because the CO2 sensor in it is using different (newer) technology that only released a few years ago from Sensirion.
(Upd: the IKEA does have lower accuracy, with ±100 ppm instead of ±30 ppm. From the SEN63C datasheet)
Worse specs? Sure. Worse value? I don't think so. Worse accuracy? Perhaps not either.
A price of 30 EUR makes this sensor really easy to pick up. For the same price as one Aranet (~180 EUR) the typical household can place a sensor in every room of the house. Which provides far more accurate readings for the whole house than just one high-end sensor in one room.
I have one IKEA Apstuga on my desk, sitting right next to a good CO2 monitor. Since Apstuga uses worse approach (heat) rather than light as the good sensors, it diviates around +/- 100 ppm. For example the correct CO2 is 610 ppm and IKEA's sensor shows 552 ppm with is reasonably close. So the trend will be correct and the values will not be.
But when it goes over the safe limit it should be enough to decide to ventilate.
No, it is crap. Yes, it is Sensirion, but it uses a thermal conductivity sensor, which is a very indirect method of measuring CO2. One part of the sensor emits heat and the other senses it and the idea is that heat transfer changes with different CO2 concentrations. However, a lot of other factors influence this as well, such as ambient temperature/humidity (which is why the sensor incorporates measurements from an SHT sensor), but also gas mixture, etc. You only get good readings at lab conditions. Even below 1000 ppm, I would often see readings that are 300 ppm from more expensive, known-good CO2 meters.
If you want a CO2 meter on the cheap, either wire up an optical NDIR sensor like the SenseAir S88 (22 Euro) up to an esp32, which is possibly the best sensor you can get for the money (slightly cheaper version of the sensor that the AraNet4 uses). Or if you want something standalone with a display, get the SwitchBot Meter Pro CO2 for ~50 Euro, which uses a photoacoustic NDIR, but is still miles better than the sensor in the ALPSTUGA. Can also be hooked up with HA through an ESPHome BLE proxy or with the SwitchBot Hub.
You can find a comparison of the IKEA sensor with other affordable sensors here:
https://danieldk.eu/hardware/smart-home/ikea-alpstuga
(Upd: the IKEA does have lower accuracy, with ±100 ppm instead of ±30 ppm. From the SEN63C datasheet)
You forget to mention that it is ±100ppm plus ±10% of the ambient ppm, which makes a big difference. At 1000ppm it's ±(100ppm + 0.10*1000) = 200ppm and that's only in an environment with 25C, 50% RH, and 1013 mbar. So, that does not tell you much, given that thermal conductivity is very sensitive to environmental factors.
if you just want to know if CO2 is too much, 300ppm precision is fine.
I dont need to know the exact level, just give me a green/yellow/red LED and make it cheap so I can have a sensor in every room
No, it's not. You generally want to ventilate an office when you reach 1000ppm, but then the IKEA will often warn you already at 700ppm. 700ppm is fine.
"Generally" is a vibe measurement to begin with. You won't notice any difference at all between 700ppm and 1000ppm. It's once you start hitting 2000ppm you are getting noticeable brain fog.
Had bad ventilation in my old apartment (built 1888) so got a co2 monitor. Started feeling the effect at 1100-1300ppm, so would open it in home assistant and check, never below and never above really. During winter when it was -10 so couldn't keep the window open all the time.
I disagree. I feel a very steady and progressive deterioration starting at 600 ppm. It becomes significant at 800 ppm. The studies back up the latter threshold.
Unfortunately it will be hard for you to know how much of that effect is placebo. Unless you tested this with some kind of double-blind setup.
You're not wrong, but indoor CO2 at these sub-1000 levels is a useful proxy metric for bioeffluent VOCs which are an objectively tiring subset of total VOCs. Ventilation lowers both. This explains the observation better than nocebo theory. See https://www.aivc.org/resource/effects-carbon-dioxide-and-wit...
You would not notice a difference if you weren’t checking the CO2 ppm. You primed your brain to ‘feel’ the effects of higher CO2 by reading a study and are experiencing the nocebo effect.
If it makes you feel better I don’t see a problem with it.
Indoor CO2 is likely overrated here at these sub-1000 levels but it's a useful proxy metric for bioeffluent VOCs which are a tiring subset of total VOCs. Ventilation lowers both. This explains the observation better than nocebo theory. See https://www.aivc.org/resource/effects-carbon-dioxide-and-wit...
You generally want to ventilate almost continuously, so if a circulation fan kicks on at 700 instead of 1000 that's really not a big deal.
you assume that the error will always be in one direction
and if sometimes you ventilate a bit sooner than required, at 700, what?
businesses will not put $200 meters in every room
Have you looked at the prices of meeting room furniture? A $200 meter is not a significant cost measured against what it costs to furnish the room in the first place. It only becomes significant is you treat it as a line item disconnected from the room it's in
businesses will not put $200 meters in every room
There are good $50 Euro meters. Besides that, I am not sure if that is true, at my wife's workplace, they put high-end CO2 meters in every larger room where multiple people meet. Admittedly, this was during COVID, so a lot of organizations were using CO2 levels as a proxy for finding whether a room was properly ventilated.
Presumably there is still the need to ventilate. So the concentration can also be measured more centrally. That is how the mechanical ventilation unit in my house works. For both humidity and CO2.
$200 is nothing compared to the lost productivity.
You put one CO2 sensor in the return air duct and tie it to outside air control.
But if I open a window at 700ppm, so what?
Suddenly there's not enough CO2 in the room and you get overly awake! Bummer! /s
I got the ikea sensor, I’d say it’s way more accurate than you need for personal use. I wouldn’t use it as a scientific instrument but it’s well good enough to see if the room is ventilated enough.
I was shocked to see just how fast CO2 climbs while in a room, and how just opening the window just a crack was enough to restore the room to baseline co2.
The thing runs on usb 5v so the power consumption is negligible. It also plugs in to home assistant great.
I have HA send me a notification to ventilate my office when the air reaches 1000ppm CO2. The IKEA ALPSTUGA is often off by 300ppm even under 1000ppm. If I'd use it, I'd be getting notifications at 700ppm.
It is a thermal conductivity sensor, which is a very indirect way of measuring CO2 and is very sensitive to environment factors. You only get somewhat good readings in lab conditions.
Don't by the ALPSTUGA for anything but very rough trends, there are much better affordable options.
Within 300 ppm is more than good enough. Realistically 1000 ppm is not that bad. The average meeting room is multiples of that.
Also in my experience it’s much more accurate than that.
I notice that thinking becomes less clear when going above 1000ppm, so I let HA send a notification at 1000ppm. With ALPSTUGA it would send already at 700ppm. By the way, above 1000 the divergences become even larger due to the inaccuracy also being 10% of the ambient CO2 concentration (in optimal circumstances, probably larger IRL). So, suppose you want to be notified at 2000 ppm, the IKEA sensor might already do so at 1500 or 1600 ppm and it continuously drifts, so it's not like you can use a particular offset.
Besides that, what's the point? There are much better meters in a similar price class. As an additional benefit, they can last months or up to a year on two AA batteries.
ALPSTUGA is an inferior product.
Can you recommend some?
Mentioned two here: https://news.ycombinator.com/item?id=48783879
>With ALPSTUGA it would send already at 700ppm.
"oh no I am getting too much fresh air"
I get your point but come on.
Can it work with Zigbee network or is Matter/Thread required?
I'm using a bunch of IKEA's "smart home" stuff, all via Zigbee+HA, works great. Look for the Zigbee icon on the package, and the pairing for Zigbee vs their own home controller might have slightly different pairing sequence on the device, otherwise it just seems to work.
ALSTUGA does not work with Zigbee.
They recently overhauled their lineup and replaced all Zigbee devices by Thread + Matter. Some of the new devices (mostly those who support TouchLink, e.g. some of the lights) have a secret pairing mode with which you can use them with Zigbee, but it's only a subset of the new products.
> They recently overhauled their lineup and replaced all Zigbee devices by Thread + Matter.
Uuh, seems not keeping up with social media finally backfired. That sounds horrible! So far IKEA been a great experience when it comes to HA+Zigbee stuff, and I started buying stuff relying on they'd keep just keeping up with that, really sad to hear they've changed course.
The "secret pairing mode" stuff sounds the same as currently/before though, but they only do so for a subset is new and hope they again change their mind.
Thread is significantly better. Zigbee relied on proprietary hubs and apps or hacky work arounds. Matter over thread devices don't need a brand specific hub or app. You can literally control the new ikea products direct from a modern iphone which includes a thread radio, no hub, server or app required.
If you already own the ikea hub, they secretly put thread radio in it which was just sitting unused in preparation for this range.
It's complicated. Matter over Thread is indeed nice in that it you only need generic Thread and Matter servers. It also makes it easier to share credentials between ecosystems. Thread itself is also a pretty nice standard technically.
There are also strong downsides though, one is privacy and future cloud lock-in. Zigbee is fully local. Previous Thread standards added the option for NAT64 so that Thread devices can access the internet and there were some Thread + Matter devices that already require internet access for full functionality (IIRC some Nuki smart locks, but I might misremember). However, Thread 1.4 also adds support for Thread devices to get a globally routable IPv6 address. The Thread 1.4 whitepaper is pretty blunt about what this enables:
Simplified Cloud Integration: Thread devices can now seamlessly connect directly to cloud services, enabling remote control, monitoring, and over-the-air firmware updates.
https://www.threadgroup.org/Portals/0/Documents/Thread_1.4_F...
The fact that Thread and Matter are strongly pushed by Google, Apple, etc. should tell you enough.
Now, a TBR may simply allow you to disable NAT64 or globally routable IPv6 addresses (e.g. Home Assistant's addons), but many consumer implementations don't. E.g. the Apple TV is a Thread Border Router and does not allow disabling NAT64, so Thread devices can access the internet, send analytics, and can be cloud-controlled.
Also, the ecosystem is still pretty immature, as a result of which you can encounter issues, typically resulting in unstable device connectivity. E.g. TREL does often does not work well. Apple has some hacks to fix most of the issues, but it only works well between Apple devices. So it's generally the best to avoid combining multiple TBRs into the same network.
> Thread is significantly better.
Better than what already exists and is deployed? I dunnno, hardware already in use always beat "hardware conceptually better but I don't have it", that's why Zigbee is better, for me. Protocols much like everything in the world, isn't correct/incorrect or universally "better", it's all down to use cases.
Personally, as someone who started to rely on IKEA providing Zigbee devices, Thread is obviously worse, because 100% of the devices I have are already Zigbee and not Thread.
Ikea preemptively sorted this out by putting thread radio in their hubs years before rolling this out. There's also thread radios in the latest chromecast, apple tv, and loads of other products. If you have a single thread border router in your house from any brand you'll be able to connect to any thread device from any brand. Phones can also directly control thread devices without needing any network or hub.
It's a vastly better system and the transition period is so smooth because the smart home companies have been deploying the thread hardware for years before anyone started using it.
smart home companies have been deploying the thread hardware for years before anyone started using it
Also worth mentioning that many modern Zigbee radios can also be Thread thread radios using different firmware. There are even multi-PAN radios that can do Zigbee and Thread at the same time. Some smarthome hubs use multi-PAN (e.g. Homey Pro), but it's generally recommended against now because of lower reliability.
The same applies to devices, e.g. some of the new IKEA devices work over Thread or Zigbee (Zigbee pairing is triggered using a non-documented sequence, presumably they added support for TouchLink). Or e.g. the Aqara FP300, which can be flashed with Thread + Matter or Zigbee firmware. It works because the same radio can be used for both protocols.
This wasn't true for zigbee either. I used a zigbee usb stick with home assistant, could use any stick that was supported.
Yeah, I bought a bunch of INSPELNING smart plugs when they were clearing out the inventory. The new GRILLPLATS switches are more compact though, which is nice.
It’s part of the new range which is all matter over thread only. The existing ikea hub can do thread though.
> The thing runs on usb 5v so the power consumption is negligible.
There’s a huge leap from that to the power consumption being low enough to be integrated into a smartphone, as demanded by OP.
I don't think power use is the issue. I have this cheap CO2 sensor: https://www.domadoo.fr/en/devices/5882-heiman-zigbee-air-qua... which draws 0.5W. This includes thermometer and humidity sensor, Zigbee transmission, and acting as a Zigbee router, but it gives us an upper bound. It also measures continuously (picks up someone breathing on it within 10s), which is overkill. A phone could measure CO2 levels once every 10 minutes which would average under 0.01W, so that would work.
However, this assumes the sensor would fit in a smartphone, which is not a given. And these things need air flow. And they also wouldn't work while the phone is in a bag or a pocket.
>A phone could measure CO2 levels once every 10 minutes which would average under 0.01W, so that would work.
Not sure about that, at least NDIR sensors have to be at certain elevated temperature to work and they do some preheating when you turn them on from standby.
So it's not possible to just measure less often as then energy would have to be spent on heating the sensor.
Ruuvi Air[1] seems to be close to the middle in both price and CO2 measurement accuracy between aranet4 and the IKEA device. I don't have personal experience with Ruuvi Air specifically, but have been using their cheaper Ruuvi Tags (that don't measure CO2) for temperature, humidity and air pressure measurement at home and office.
[1] https://ruuvi.com/air/
> I also don’t know how much electricity they pull.
It can't be much, since the Aranet 4 can run for years on 2 AA batteries.
Is it a tually lower oxygen in the blood that's the problem, or higher co2? I'm not sure if having high co2 automatically implies lower oxygen, I have no idea at all but feels like it may not necessarily be strictly. Linked. Also, are the cognitive issues of low oxygen the same as high co2 or do they produce different effects?
From what I learned from Apollo 13, even with O2 in the air, CO2 can still be poisonous.
There is one in the EcoBee Premium and we use it to automatically drive our HRV (heat recovery ventilation.).
It is better to have it in the HVAC system than in your phone anyhow:
https://ben3d.ca/blog/upgrading-hvac-control
I built a conference badge with a proper, laser-based CO2 sensor.
It didn't work very well because just by virtue of being near me all the time, it didn't get a very good measure of the average room contents.
> Raising awareness is the only real solution.
You'd have to raise awareness on every single person in the room and them sustain pressure to the organization in order to have proper CO2 levels in the room/organization.
And then you have to align every other person on every other organization to do this as well and hope for the best.
Or, you can do the right thing and have the state introduce regulations
I don’t think that’s right. If people have an easy way to measure the levels, and they can see something on their phone like ‘you spent 8 hours today above 2000ppm CO2’ then the room will care a lot more than it did before, and people will be able to quickly see whether they have improved things. At my employer, I think it took us around 1000 employees until we randomly hired someone who happened to care a lot about CO2 levels and I think they managed to cause a decent increase in the amount that the company cared / thought about levels (this was around the end of Covid though so part of this may have been due to using CO2 levels as an indication of insufficient ventilation/air filtration).
Depending on the state, newer buildings do have regulations on air ventilation and quality.
The rooms being discussed here are mostly ones which would have been built before this was taken more seriously. Classrooms, older office buildings, etc.
NYC is full of buildings which would never pass any code today but are still happily occupied. It’s a trade off, I think.
Can't you just open a window a bit?
In lots of modern office buildings you can’t.
ah, sadly that was in my last modern one. Thankfully we can open the windows in this one :)
Best solution.
I can just imagine the horrors and skin crawls that your last sentence has evoked in some people's minds. Not the state!!
But seriously, so much care needs to be taken here. OK, well "care" at least. Employers certainly would benefit from scrubbing CO2 from the air, in terms of productivity. I'm willing to bet that with central air it would be quite easy, and even with heat and AC off, lots of places still circulate the air regardless.
So the central place to scrub is already there.
But then you have other issues. Such as, will your body adapt to 8 hrs of reduced CO2, and then you become torpid and barely awake when not at work. Such a horrid thought, that is to me. And what if employers learn that the tiniest boost of O2 helps too! Now your body becomes accustomed to that, and what are the long term effects there?
I can personally envision myself being concerned. I guess the legislation could be crafted to "the same CO2 levels found just outside of downtown city core" or some such blather. Maybe even same for O2. So that you're at least pegged to something normal for the area.
Maybe that's where the state could come into play. A simple, highly accurate monitoring station which has an API to be polled.
Come to think of it, CO2 and O2 rates fluctuate during the 24 hour cycle. Trees need O2 to live, but only produce O2 during the day. And so differing amounts of light might mean up and downs in these numbers. It may be another circadian rhythm. Getting it the same as in a nearby forest, might be the healthiest thing of all.
In practice, one would use energy recovery ventilation to exchange air with outside rather than a CO2 scrubber (not clear if you actually meant a scrubber).
The place to look is existing codes for ventilation. Exempli gratia: https://dos.ny.gov/system/files/documents/2020/09/2020-mcnys... (see PDF page 46). Regulations to enforce outside air being brought into human spaces already exist.
I have been in some office buildings in United States which had CO2 monitors in each meeting room, and the ventilation would engage to control CO2 below a set level. We would entertain ourselves by exhausting our lungs onto the sensors to trigger the ventilation system.
I should have said it more clearly, I just thought HN would take this stance regardless. If you tell an employer to ensure CO2 levels, and it shows an improvement in productivity, employers may think "Hmm. Let's improve this further!" and add O2 as well.
In terms of outside air, a lot of US cities I think would not benefit from that, all that much. Especially during certain parts of the day, with a lot of smog.
But regardless, all that entered my mind was "Once employers are required to add any form of scrubbing, and perhaps O2 injection, they'll over do it for optimal employee output." Regardless of whether it's helpful once the employee leaves the workplace.
I'm not against this, I'm just actually saying the regulation should be locally defined.
You’re talking about oxygen like it’s California Rocket Fuel or meth.
Controlling indoor CO2 is important, but it's a proxy metric for the escalation in indoor bioeffluent VOCs which are a tiring subset of total VOCs. This is why scrubbing indoor CO2 will by itself never produce the pro-cognitive result you want. See https://www.aivc.org/resource/effects-carbon-dioxide-and-wit...
Scrubbing indoor CO2 is sensible only when you want to go below the outdoor CO2 level, not at levels above it.
It is not that complicated. You need to introduce CO₂ threshold levels that make sense from a medical standpoint. Then you need to enforce them in the same way other basic environmental regulations or worker rights are enforced in regions of the world where these work.
The main question is: If your workplace, city, whatever forces you to work or live in an harmful/unhealthy environment, do you have any realistic course of action to improve the situation? In the US you would call this (gasp) regulation, I would call it a basic human right.
If we talk about stairways, nobody complains about building regulations that mandate handrails. CO₂ levels are not totally different.
I was looking at CO2 sensor module boards this week and the sensors themselves are quite large and the floor price is $15ish.
Those $15 ones are also straight up scams. They just estimate (lie) for the readings based on other sensors.
And I believe the accuracy is also not great on these cheap ones. The product in the OP's photo costs $200 where I live! And ISTR finding the sensor itself contributes a lot to this cost.
IIUC they also need fans. The one I have in my home has one that's actually integrated into the sensor unit.
This would probably be the biggest awareness thing tech could do for climate change as well.
CO2 and all other air quality indexers have to be very carefully calibrated regularly. It's not some slop you can just throw into a consoomer cheap iot device.
Article author completely ignores this for the obvious reasons.
For the purposes of indoor ventilation monitoring you can calibrate by occasionally exposing the sensor to fresh air. Either taking it outside or just the room not having people in it. The sensor will treat the lowest reading it gets as 400ppm since this is what outdoor air is.
A sensor mounted in the office will get calibrated every night when the office is empty.
The outdoor CO2 is rising every year. It is not fixed at 400 ppm. The calibrations you speak of are fake. A good sensor can be expected to remain within 10% of reference for ten years.
The outdoor CO2 is rising every year. It is not fixed at 400 ppm.
But close enough for most purposes. We aren’t doing laboratory measurements here, I just want to know whether or not to open a window.
You don't need to routinely calibrate a good device at all for that purpose. It already will maintain a reading within 10% of the real value. If it's not doing that, it's a bad device. It's very possible your calibration process will actually miscalibrate it and increase the error. Already the outdoor CO2 level is 430, not 400, so you'd be introducing at least a 7% error by calibrating it to 400.
What I do at home is I have multiple meters bought over the years, not all at once. If one of them is too deviated, I can replace it, but this deviation has never happened in the last five years. It did happen once about ten years ago with an old model.
Not really. For ventilation purposes, a good sensor remain within 10% variation for nearly ten years. We are not running a controlled science experiment here.
Apple watches already have a blood-oxygen sensor so it's covered, albeit indirectly.
I don't think that's true at all. Capnography, the measure of carbon dioxide partial pressure is wholly separate from pulseox:
> Pulse oximeters have some limitations. They can only employ light at two wavelengths. Thus the devices can only distinguish between hemoglobin and oxygenated hemoglobin. When carboxyhemoglobin and methemoglobin are also present, there are two additional wavelengths required for differentiation. In the presence of elevated carboxyhemoglobin levels, pulse oximetry overestimates the true saturation of oxygen as carboxyhemoglobin binds with a higher affinity than oxygen. In the case of carbon monoxide poisoning, the absorbance spectrum of carbon monoxide is very similar to hemoglobin, which results in a falsely high level of oxygen (overestimation of oxygen saturation) ...
https://www.ncbi.nlm.nih.gov/books/NBK539754/
>Pulse oximeters have some limitations. They can only employ light at two wavelengths
Why only 2?
I don't think that's safe to assume at all, for two reasons:
1. CO2 has effects on the human body of its own that aren't simply a lack of oxygen, and vice-versa. [0]
2. The baseline proportions involved aren't close, so even doubling CO2 isn't going to show up easily as a large swing in in oxygen%.
For example, the article references a study where the CO2 proportion going from 0.04% -to 0.25% correlates to mental problems.
Even if the watch could sample atmosphere directly, is it sensitive enough to detect a shift from 21.00% -> 20.79% oxygen?
As it's estimating oxygen in the owner's blood, it might not detect anything different at all... not if the owner's body has already compensated by breathing harder or by "underclocking" their brain to make dumber decisions.
[0] https://en.wikipedia.org/wiki/Asphyxiant_gas
> The article references a study where the CO2 proportion going from 0.04% -to 0.25% causes mental problems. In other words, a difference in 0.21% of the air.
I'm finding that pretty difficult to believe, to be quite honest with you.
And before you say "aha, carbon dioxide brain fog!" consider that I'm about a mile from the sea with a 40mph onshore breeze. This air is about as oxygenated as it gets.
It makes a lot of sense actually. You get severe symptoms when CO2 makes up only a couple % of the air. And can become fatal at like 5%. There’s not like a hard line where you suddenly die, it’s a gradual thing. It very much makes sense that we’d notice minor symptoms at a few thousand PPM when it only takes like ten thousand to feel it severely.
1% (10,000 ppm) is enough for the person to become aware something is odd through drowsiness or an elevated heart rate.
I don't think it's too far-fetched for a quarter of that to cause subconscious cognitive effects, that could be measured in tests.
I got a monitor as we had an old apartment with bad ventilation. When I started feeling it I would check and it was always around 1200ppm and would open a window for a bit. Outside air is around 420ppm, but that's not the problem, enclosed and badly ventilated rooms are if you spend a few hours in there.
I’ve had a Co2 monitor for years. I get headaches from increased Co2 levels plus the lethargic state. It’s been revolutionary - including on long drives where it’s def saved me from crashing.
Personal opinion, you can see cognitive decline at 1000 ppm. Not “ur a zombie” but it’s there. Airflow has vastly improved my life.
Another personal opinion - the coporate stupidity and inane behavior we all see tracks back in part to Co2 levels turning people into quasi zombies. It’s a lot easier to just not care, and things don’t click like they should, when in higher Co2 environments - pushing everyone to rote, process, unthinking approaches. Sounds familiar?
As a high school teacher, I first noticed this effect when I started using a CO2 monitor in my classroom as a proxy for air freshness during COVID. The CO2 levels in our supposedly "no problem with the air" classrooms shot up to 2000 ppm within minutes of the start of school and stayed there all day. Kids weren't checked out ONLY because I teach mathematics. They were breathing bad air, too.
Worse, when I brought the monitor home, I found the levels there were elevated even with no one home and surpassed 2000 with just two or three of us in a room.
The good news is that I stopped worrying about making my house "tight" for the sake of energy efficiency. I keep some windows cracked all year and don't worry about how tight the door seals are.
> The good news is that I stopped worrying about making my house "tight" for the sake of energy efficiency. I keep some windows cracked all year and don't worry about how tight the door seals are.
The point of having "tight" houses is not (just) about energy efficiency but about air quality as well. The general mantra is build tight, ventilate right. It's why modern building codes mandate air tightness and having ERV/HRVs.
By having a leaking house you do lose efficiency because in summer the air you paid to cool goes out and the hot-humid comes in, and in winter the air you paid to heat escapes and the cold comes in. But in addition to temperature (and humidity/moisture) you also get things like pollen, brake dust, (depending on your region) wildfire smoke, etc.
By ventilating right with ERV/HRV, you remove stale air and bring in tempered fresh outside air that you filter before distributing throughout the building. Air quality is also why 'spot ventilation' is also generally mandated at certain locations like over a cooktop/range in the kitchen, and in bathrooms (where the primary purpose is not taking care of smells (though helpful), but rather moisture from showers/baths).
* https://www.youtube.com/watch?v=CIcrXut_EFA
* https://www.youtube.com/watch?v=UTBNNhUH5V8
* https://www.greenbuildingadvisor.com/app/uploads/sites/defau...
* https://www.youtube.com/watch?v=lFfH1ljQgN07&t=3m14s
I would not want to live in a city where I have to be careful letting in outside air or going outside because there's too much air pollution...
> I would not want to live in a city where I have to be careful letting in outside air or going outside because there's too much air pollution...
1. Not living in a city (polluted or otherwise) still does not solve the problem of letting out cooled air and letting in hot-humid air in the summer, and letting out warmed air and letting in cold air in the winter. If your CO2 is high are you going to crack open a window when it's -10 outside? Or in the middle of a heat wave (esp. if you have AC and paid to run it to cool your house).
2. Not-city living also has pollen and other allergen leakage. You're also more likely to get wild fire particulates in less urban areas.
Building tight and ventilating right is applicable in all locations and all climates.
And in the extreme case, if you believe the outside is the healthiest environment, live in a tent or under a tarp. :) Buildings were invented to have a separate outside and inside, and leaky houses reduce the effectiveness of that separation.
Even if you live in an air quality paradise, it’s not ideal for your indoor air to be the air that manages to sneak through all the little cracks in your structure. Especially if you have cold outdoor temperatures, indoor humidity such that the outdoor temperatures are below the indoor dew point, and airflow through the walls that can lead to condensation and possibly mold in those walls.
Your indoor air should enter through windows or intentional intakes, not incidental gaps.
> Even if you live in an air quality paradise, it’s not ideal for your indoor air to be the air that manages to sneak through all the little cracks in your structure.
Small cracks are also things that critters may be able to get through.
Living in the countryside won't save you. I spent my childhood in a rural area and our house had the misfortune of being situated on a steep hill, so at all hours of the day and night you'd have cars and motorcycles and tractor trailers revving their engine to get up that hill. Every year we'd have to powerwash that road-facing side of the house to clean off the accumulated black grime, and sleeping with my window open, which faced that same road, always caused me to wake up raspy and hacking. Cars are a problem no matter where you live.
Not everywhere is LA.
How much does implementing all that cost? What degree of benefit does it offer over simple window in situations where those concerns are negligible? What other benefits to human life could be procured with that money?
It just boggles the mind that people feel emboldened to only look at one side of the equation.
> Not everywhere is LA.
> How much does implementing all that cost? What degree of benefit does it offer over simple window in situations where those concerns are negligible? What other benefits to human life could be procured with that money?
Everywhere not being LA is actually an argument for ERVs/HRVs. The weather in LA (AIUI) is fairly even and consistent and it is probably fairly easy to just open a window.
But if you're in Texas with high humidity, or Arizona with high heat, or north of the Mason-Dixon line where people get winter, it's kind of hard to open a window when it's 0 or -10 outside. If you have stale air (perhaps as measured by high CO2) what are you supposed to do?
Over the July 4, 2026, weekend it's supposed to get >90F/>32C on the east coast of the US: do you want to open your windows and let all of that heat in? Especially if you already have an AC unit so paid to run it get your home's inside temperature down?
If you have a place with ducts, you can purchase an ERV and tap into that for US$ 1000:
* https://www.hvacquick.com/products/residential/HRVs-and-ERVs...
or even less:
* https://hvacdirect.com/air-cleaning/erv-air-exchangers.html
And even in milder climates (like LA), have the ERV suck in air from the outside through an MERV 13(+) carbon filter, and not only do you deal with things like wild fire smoke, but wild fire smell:
* https://www.greenbuildermedia.com/blog/wildfires-make-indoor...
* https://shop.aprilaire.com/products/aprilaire-513cbn-odor-re...
It is possible to make your indoor air cleaner than the air outside.
>The good news is that I stopped worrying about making my house "tight" for the sake of energy efficiency. I keep some windows cracked all year and don't worry about how tight the door seals are.
You could also install an energy recovery ventilation (ERV) system.
Your comment is suspiciously missing the part where your students performed measurably better after decreasing CO2 concentration.
Assuming they had any control over the ventilation in the room.
I’m not saying this isn’t a legitimate concern but this really seems to have exploded amongst the tech community as the next obsession.
I see this pop up on X every few weeks. Is the concern about this really based on actual science? Is there empirical data proving people are less productive or are damaging themselves as a result of heightened CO2 levels? And I don’t mean observational epidemiology studies.
Anecdotal, but I'm convinced it screws up sleep quality. I'd just accepted for the longest time that waking up groggy with a slight headache and tired was the norm until I put a CO2 monitor in my room. With the door closed, it climbed up to 1500ppm in under an hour.
I'm certain many people are sleeping in similar conditions without realising and ventilating their rooms properly or leaving the door open.
> Anecdotal, but I'm convinced it screws up sleep quality.
It absolutely does.
>I'd just accepted for the longest time that waking up groggy with a slight headache and tired was the norm until I put a CO2 monitor in my room. With the door closed, it climbed up to 1500ppm in under an hour.
Same experience here. Opening windows just a bit totally changed my sleep quality.
Higher CO2 vs. free cat access at 4:17am. No win scenario!
I have this same challenge!
Also, moved all of my lovely oxygenating plants like lillies out of the room because they are toxic to kitty.
And window.
An open window means kilowatts of energy wasted. All the air I spent money cooling will just leak out. It also means all the pollen will be let in.
IMO it's something where an intervention is often cheap enough that it's worth it even without great evidence.
But also bear in mind that regardless of "are we operating at max effectiveness", OSHA sets a legal limit of 5000ppm in a workplace, and that's about _safety_.
This article is talking about keeping levels below 1000 which is a very high standard IMO (still arguably justified given the studies mentioned). But if you are in a poorly ventilated home office you could easily hit 3000. At that point you are closer to "illegal in the US" than "earth's atmosphere".
So yeah even if you are unconvinced about micro-optimising your CO2 levels there's a very long established argument in favour of at least paying _some_ attention to it.
It's not even that hard to optimise at home. I've found simply leaving the door open to the rest of the house causes the room CO2 to not elevate much over baseline outdoor readings. Or just opening a window just a crack will rapidly remove all excess co2.
The real problem is offices and meeting rooms where you have 10 people in a small box for hours and windows that don't open.
Any affect from CO2 specifically seems weak. Clean air in broadly good though, and high CO2 is a good proxy for stale air. So I’m always supportive of people caring and paying attention to their air.
Along the way they’ll either learn about or accidentally mitigate other ills like radon, nitrous oxide from stoves, diesel particulate’s impact on test scores, etc.
We assume sometimes that everybody experiences this in the same way, but a lot of people might be super-sensitive to it, and others completely immune. It is quite possible that the ones obsessing about it are the sensitive ones, because they feel it much more.
I agree it seems like a concern fad. I talked about it once with my brilliant MIT-educated 20 year Navy submariner brother-in-law and he didn't commit one way or the other but did say submarines have CO2 in the low thousands.
You'd think (hope) if there was a big effect here on performance, the relatively cheap/easy solution of maintaining lower CO2 would be standard. I know people think of the military as dumb grunts who you don't want to think, but he was one of the four department chiefs onboard (Weapons, Nav, I forget the others) and they have pretty substantial responsibility to make decisions on their own.
It's peak HN meme material because 1) it (allegedly) affects your intelligence which everyone here values highly 2) you can measure it, it's a number 3) requires tech to measure it
So perfect for HN, you can obsess over numbers and tech and how to measure it endlessly and overhype the significance to trick yourself into thinking you're doing something useful.
You get to have your cake and eat it, no wonder everyone loves this topic.
(Also if you're a doomer type you can link this in with rising atmospheric co2 levels for extra points)
Also this is finally a great reason to order a dozen Arduinos + sensors for a domestic IoT project.
Sounds like a positive thing :)
Not necessarily.
Worst case people open windows without effect, no?
Opening windows can bring in pollen, dust, humidity, noise, and a lot of energy loss during cold winters and hot summers.
In a bedroom it might be worse than the elevated CO2 problem.
That’s a bit of a dramatic way to describe opening a window.
I've been designing my own ERV system for the house and have been weighing all the options, so I had this list in my head. Nothing dramatic, just the reality. We have allergies and like sleeping in a cooler bedroom.
As dramatic as having a runny nose and sneezing all day, having to overuse your asthma inhaler.
Is that really dramatic, or just the reality that needs to be considered in a cost-benefit analysis? Are you a hay fever truther?
Nope. Opening windows is very often disallowed - whether socially, or you'd need a hammer, or the space doesn't have windows. Or opening windows would have other downsides - letting in rain, or too-hot/too-cold air, or pollution, or ...
Can't let those stupid workers open a window and ruin the efficacy of the precisely engineered hvac system that lets the building hit LEED Platinum or whatever
Yeah. But even when you can, how many bosses might forbid it - because there's already too many arguments over the thermostats, or it's kinda noisy outside, or HR warned 'em of lawsuits for doing that when the air pollution numbers are elevated, or whatever?
Perhaps HR should be warning them of reduced productivity and lawsuits when the CO2 concentration is elevated.
That is also my impression. CO2 build up provides a neat opportunity to carry around sensors, track something, display graphs and formulate quantifiable sets of rules. And also is a (more or less) interesting topic to discuss with others. Seems highly appealing to a large part of the crowd here. Personally, I only observed that some people are obsessed about having always one or more windows open but I never personally experienced any non-obvious problems with CO2 buildup. At some point the air is just smellably getting thick and then you just air out. Wouldn't need sensors for that.
The article links into two controlled experiments.
https://www.youtube.com/watch?v=1Nh_vxpycEA
This is not a peer-reviewed study. It's a Tom Scott youtube video.
And the sources he gives in the video's description are really bad.
Are we not peers to Tom Scott?
I appreciate Tom as an educator, but he's not particularly an authority on anything.
Only if you watch it on Peertube. The link is explicitly YouTube.
Somewhat unrelated, Tom also did a great video where he was put in a low oxygen environment. Similarish effects, differentish cause.
how can you detect without a study if CO2 meters are basically nowhere?
https://pmc.ncbi.nlm.nih.gov/articles/PMC4892924/
I’ve lived in Australia and France and I’ve always attributed the taller size of Australians to the excellent state of their ventilation in buildings. Vents (and rooms themselves) are systematically bigger than in France, and if you live in a healthy environment, with meat, lots out outdoors during teen age, and correctly ventilated classrooms during their 20 best years, it makes no secret to me that they grew bigger.
Meanwhile in France we heat classrooms by stacking 35 kids in a confined space. It saves on heating, plus condensation that makes windows opaque helps pupils concentrate on the blackboard, as teachers said during my childhood.
> I’ve lived in Australia and France and I’ve always attributed the taller size of Australians to the excellent state of their ventilation in buildings. Vents (and rooms themselves) are systematically bigger than in France
The average male height in France is 178.60 cm, while in Australia it is 178.77 cm:
* https://worldpopulationreview.com/country-rankings/average-h...
Some sources even have France being higher than Australia:
* https://ourworldindata.org/human-height
> it makes no secret to me that they grew bigger
That sounds like something you made up to justify your beliefs…
So how does any of that relate to height? From what data I could quickly find, both countries are essentially equal in average height.
France is indeed ridiculously bad at ventilation (not to mention air conditioning). Restaurants, offices, even gyms - most have bad to non-existing ventilation. Coming from the States this is just insanity.
I mean try it for yourself... open a window a bit unless you live in a hellhole.
Also go for a walk, unless you live in a hellhole.
Having CO2 sensors is mostly useless.
In Quebec province in Canada, they added CO2 sensors in all the classes in all the schools after covid. Now what? Having data does not change anything if nothing is done.
If instead all the millions invested would have gone into adding air exchangers, now that would actually do something.
And that is assuming that CO2 levels really have an impact. From the last time I researched the subject, I found that there were few studies showing an impact.
For context, from what I remember, in submarines the CO2 levels are usually between 10 000 ppm and 20 000 ppm. Very far from 1000 or 2000 ppm.
Also, CO2 sensors are usually pretty bad. I work in HVAC and I hate calibrating them, the readings are not very consistent. Leave them alone for a few years and a good percentage will simply output bad readings.
Then you see things like a teacher leaving the windows open in winter because the sensor says 2000 ppm all the time instead of realizing the problem is the sensor. (CO2 levels should go back to atmospheric levels over the weekend for example at about 450 ppm)
I very much doubt submarines operate that high
The ISS runs at 3000-6000ppm CO2. over 7000 is dangerous
over 7000 is dangerous[citation needed]
I found 3-11k as regular levels, with no impairment known of. So acclimatization can happen?
>Having CO2 sensors is mostly useless
I got one because old apartment and bad ventilation. Was able to open a window when I felt the effect before, but now I can get an alert earlier. Since getting it I could consistently feel the effect at around 11100-1300.
I'm in the indoor air quality business. This is real.
A good way to think about CO2 is as a proxy for dirty air. CO2 is easy to measure but what it really means:
The next breath you take has: - already been inhaled and exhaled by others several times. - contains remnants of their farts, burps, off-gasing from everything they are wearing, have, everything in the room, etc. - may have presence of other gases like radon in the winter, mold spores, g-d knows whatever else. - co2 itself has negative effects but mainly it's a signal of what else is probabilistically in your air, poor ventilation.
Florence nightingale the inventor of modern nursing wrote that making indoor air as close as possible to outdoor air (without freezing the patient) is the best and most overlooked input to wellness. I believe this is still true.
Weirdly there are people who for some reason are hell bent on denying the air quality as an input to health and cognition. The simplest way to reason about it is: the argument for organic food is the less toxin-like stuff in it the better. Same for filtered or spring water. We often fail to quantity the impact exactly but we (logically) know that less toxin is better. For some reason we hold a much higher bar for "blaming the air" which doesn't make sense.
By volume we consume exponentially more air than food or water, and it enters the blood stream faster and more directly so obviously it impacts us. The EPA ranks indoor air quality as a top risk.
Ironically we are obsessed with outdoor air quality and if you have allergies to things like pollen that's a real concern but in most cases outdoor air is the baseline for what's indoors + other shit is added.
I find that there are people who say "wow air quality here is bad" and there are people who say "oh man I'm tired lately" without being able to attribute it, but I don't ever see anyone thriving in what is objectively bad air.
Sorry forgot the thing most directly related to the article. Harvard did a study on air and cognition (Google Harvard cogfx) - here's the Gemini summary which tracks with my research:
Study 1 (Simulated Office): Participants in optimized "Green" and "Green+" office environments scored 61% and 101% higher, respectively, on cognitive function tests compared to conventional office environments.
Study 2 (Buildingomics): In a real-world analysis, occupants of high-performing, green-certified buildings had 26% higher cognitive scores and slept better than those in high-performing but uncertified buildings.
Home/Work Study: Researchers tracking remote workers found that suboptimal indoor temperatures and elevated CO₂ (indicating poor ventilation) directly harmed creative problem-solving and cognitive processing.
Submarines operate in the 1000s of PPM CO2 range and the sailors aboard generally do not experience any ill effects. This was tested and no deficits were found even at 15,000 PPM: https://asma.kglmeridian.com/view/journals/amhp/89/6/article...
A major confounding factor is everything else in the air. Humans produce lots of different gases, and CO2 is usually a proxy for the overall concentration of our effluent gases. But in a submarine, or in some buildings, there are gas filters (usually carbon, possibly with various modifications) that can remove or destroy some of these gases but have no effect on CO2. So the air in a submarine at 15000ppm CO2 could be very different from the air in a an unventilated room that reaches 15000ppm CO2.
The first person to deal with this may have been Cornelis Drebbel in 1610 when he deployed the first submarine. With 4 oarsmen submerged in a leaky wooden sub, they’d have too much co2 and too little oxygen. Somehow they were able to stay for hours at a time.
Robert Boyle describes Drebbel’s use of a “chymical liquor” to refresh the air.
“Paracelſus, indeed, tells us, that "as the ſtomach concocts the aliment, "and makes part of it uſeful to the body, rejecting the other; ſo the "lungs conſume part of the air, and reject the reſt." Whence, according to him, we may ſuppoſe a little vital quinteſſence in the air, which ſerves to refresh and reſtore our vital ſpirits; for which purpoſe, the groſſer, and far greater part of the air, being unſerviceable, it is not ſtrange that an animal ſhould inceſſantly require fresh air. This opinion, indeed, is not abſurd; but it requires to be explain'd and prov'd: beſides, ſome objections may be made to it, from what has been already argued againſt the transmutation of air, into vital ſpirits. Nor is it probable, that the bare want of the generation of the uſual quantity of vital ſpirits, for leſs than one minute, ſhould be able to kill a lively animal, without the help of any external violence. And, upon this ſuppoſition, Cornelius Drebell, is affirm'd, by many credible perſons, to have contrived a veſſel to be row'd under water: for Drebell conceiv'd, that it is not the whole body of the air, but a certain ſpirituous part of it, that fits it for reſpiration; which being ſpent, the remaining groſſer body of the air, is unable to cheriſh the vital flame reſiding in the heart. So that, beſides the mechanical contrivance of his boat, he had a chymical liquor, which, by unſtopping the veſſel wherein it was contain'd, the fumes of it would ſpeedily reſtore to the air, foul'd by reſpiration, ſuch a proportion of vital parts, as would make it again fit for that office; and having made it my buſineſs to learn this ſtrange liquor, his relations conſtantly affirm'd, that Drebell would never diſcloſe it, but to one perſon, who himſelf told me what it was.“
https://sourcelibrary.org/book/philosophical-works-vol-2-boy...
I don't think you can cleanly compare this: In the study, they added CO2 to the room, while keeping O2 at normoxic levels throughout the experiment. In your meeting room, O2 levels will be dropping in lock-step with the CO2-levels rising. It may be the lack of oxygen that leads to drowsiness, not the additional CO2. But it's the CO2 levels that you can measure as a good proxy of overall air quality.
I don't think this is correct. The concentration of CO2 in air is about 0.04%, whereas the concentration of oxygen is 20%, so the partial pressure of oxygen is about 500x higher. This means that if, for example, 10% of the oxygen in a room spontaneously disappeared, it would be replaced about sqrt(500) = 22x faster through leaks in the room than a 10% spontaneous CO2 increase would dissipate. (This ignores a small effect due to the different density of the two gases).
So in practice the oxygen level can never drift meaningfully far from the atmospheric pressure, whereas carbon dioxide easily can because the pressures involved are so low.
Ok, fair points, including the sister comment, it's likely not a drop in O2 levels.
But then why can we see problems with concentration in studies of people in poorly ventilated rooms, but not replicate that when just adding CO2 to normal air? What is the CO2 that we can measure in meeting rooms actually a proxy for?
The Satish 2012 study that seems to have started this trend was a small cohort of 22 people split in 6 smaller groups where they also just injected pure CO2 in a small room. There have been several attempts to reproduce, which sometimes found no clear effect, or a significantly smaller effect.
This original study has been used to market these CO2 monitors for years, but the evidence is quite thin and doesn't support a strong effect. It seems likely that there is a small effect, and it has been wildly exaggerated thanks to a small study with N=22.
So is this all bullshit?
Lacking a large study, we can't know. Of course the CO2 meter companies benefit if people believe it is true.
Can it not just be that what happens in stuffy meeting rooms is boring? Opening the windows changes the temperature, the noise levels, perhaps the light levels ≈ adds some novelty, which makes you feel a bit more awake.
O2 is 200000ppm so if co2 goes up 400 to 2000ppm does o2 go down to 198400ppm?
If that study was of submariners, is it possible long-term high-level exposure causes the body to adapt?
I am suspicious of 0.1% having a significant effect though, given oxygen is around 20% and we naturally exhale a couple of percent CO2.
I mean that can't be right, as the body's breathing response is triggered by that amount of CO2 buildup. It's not about what's in the air. It's about what the body can take up. Maybe submariners are self-selected to be more physically fit, e.g. larger heart, lung capacity etc. to compensate.
Though that study included a 45 minute acclimation period. Appropriate for submarines, but I wonder what the results would be in the first 1 / 5 / 10 minutes.
CO2 levels will rise much more slowly to such high levels even in a small room.
... which is entirely unsurprising given that exhaled air is about 50.000 ppm CO2 and can vary by several 10.000s depending on depth and rate of breathing. I actually consider the recent wave of findings that CO2 levels as low as 500-1000 ppm measurably affect cognitive performance and well-being to be a great example of how you can prove literally anything with statistics and a sufficiently small sample size.
One key difference is that submariners are rigorously trained to operate effectively in less-than-ideal environmental conditions, whereas Bob from accounting probably is not.
could be a selection effect at work
Submarineers also are hand picked due to their great lung capacity...
Two tips: if you want a stationary CO2 meter in a room, you can make one very cheap with a SenseAir S88 sensor (22 Euro) and hooking it up to an ESP board. Flash ESPHome and you can get live statistics in your Home Assistant dashboard. The S88 is a pretty good optical NDIR Sensor that auto-calibrates by putting it in the outside air or in a well-ventilated room every N-days (N is in the data sheet). A bit more info about hooking up the S88:
https://danieldk.eu/hardware/smart-home/esphome-senseair-s88
If you want something with a display that works on batteries without spending over 200 Euro for an AraNet, the SwitchBot Meter Pro CO2 is pretty good option. It is regularly on offer below 50 Euro. It uses photoacoustic NDIR, but does not deviate a lot from the S88. You can use it without a SwitchBot by configuring it with a phone on Bluetooth. The meter works on external power and battery, but even when on battery, you can set the reporting interval to 5 minutes, which is good enough in practice. The meter broadcasts the measurements with Bluetooth LE, so if you want to get the data in Home Assistant, you can place a ESPHome Bluetooth LE Proxy in the vicinity [1]. This is an ESP32 flashed with ESPHome that listens on Bluetooth LE advertisement and forwards them to your HA instance over WiFi. Of course, you could also get the SwitchBot Hub, but what is the fun in doing that? :)
I would avoid the Ikea ALPSTUGA, it uses a thermal conductivity sensor, which is a very indirect method for measurements and it's often several hundred ppm off.
https://esphome.io/components/bluetooth_proxy/
I would recommend Ruuvi Air, its sensors are high quality, and is quite open for devs to do pretty much whatever with it. Works by broadcasting sensor data over BLE, so if you have a smartphone or a home assistant server with BT connectivity, you can display or store the data live. The iOS app sends alerts when different custom thresholds are crossed, like for co2 ppm.
They do have a gateway product, but it’s not necessary if you have HA. If Apple homekit routers supported BLE as source it would work seamlessly in the ecosystem, but a bridge software is required on HA.
As a middle ground I can also recommend this unit: https://apolloautomation.com/products/air-1
Looks like it's increased in price unfortunately but I like the idea, it's basically just what you would do as a DIY project but ready built. So you can either use it like a normal commercial product, or you can just fork the ESPHome config that's on GitHub and flash it exactly like any normal ESPHome project.
Yeah, I have heard good things about them. There are some other options that are kinda in between DIY and a product, like those by Screek Workshop.
https://screek.io/ https://shop.screek.io/products/sco-b
No recommendation though, I haven't tried them.
Thanks for mentioning that, last week I got 2 SwitchBot hub mini, 3 temperature sensors each, for 70€ total, they are really neat. Even put one in our fridge, I didn’t expect the signal to pass but it’s working :)
Will look at adding the CO2 monitoring
Edit: actually, they only sell them as part of a 6-in-1 device, with a display, and a bunch of other sensors. That feels overkill, I wish they would just sell the CO2 sensor itself
There needs to be a meter for the amount of AI writing in blogposts. Same physics, same climb, same afternoon fog.
This reads to me as AI generated. Apparently it's still good enough to the general audience to be the #1 post on HN right now though. Which is honestly a troubling signal for the state of the world...
Yeah, I clocked it as AI the moment I read "Here is the uncomfortable part". FWIW, Pangram detects it as 100% AI-generated.
https://www.pangram.com/history/c410d4b4-abfd-4ca0-b52d-db0d...
I've actually been tracking the front page of HN for AI posts for a while now: https://www.salahadawi.com/hacker-news-ai-detector
This post evaluates to 99% AI generated.
Nice! Have you considered doing a Show HN for that?
That's valuable in at least three different ways: public education, showing that most of the articles are still human-written which can be easy to forget about sometimes, and as an easy way to cross-validate my intuition when flagging something as AI-generated without having to manually run Pangram.
I despair a little bit about how many HN voters either seem to want to read slop or don't understand when they're reading it. This post is obviously AI generated from the first paragraph on, and still has 480 votes.
I've thought about it, will probably fix a few things and then do it
Yeah, it's really tiring reading Claude's output all day, every day. Nowadays I yearn for a different style.
I bought a $30 CO2 monitor a couple months ago, and it confirmed my suspicion that my home office (a normal room about 12' x 18') reaches unhealthy levels over 1000ppm after just a few hours; opening a window quickly restores levels to the 400-700ppm range. Afternoon mental fatigue solved. Highly recommended.
Fantastic, did you go for a particular "trusted" brand or just went on vibes? How should one rationally approach shopping for a CO2 monitor for home office use?
Oh this is absolutely so relevant and I wonder if there are any high quality studies that have analyzed driving performance against CO2 buildup in cars. Cars often ship with circulate air feature in the aircon, and people use it aggressively, nonchalantly at least where I live, having no idea about the dangers of possible hypoxia and sleepiness that might be inducing in them while driving. It is absolutely critical in my opinion for cars to have CO2 monitors. We put so many sensors in cars these days that this seems to be a really cheap and fairly high value of life addition that could possibly prevent accidents on roads. I keep a portable CO2 sensor in my car at all times, because sometimes circulation is not something I can avoid when stuck in traffic or when passing by a drain.
Got a firsthand experience with this. I was dropping off my girlfriend and we stopped to talk in the car, with all the windows up. Over the course of the conversation we got more and more agitated at each other until I had a thought and pulled my Aranet out from my backpack. It was >3000ppm CO2. We opened windows and within 2 minutes all the agitation went away.
To be fair, that might not just have been the CO2 dropping, but also the pattern interrupt + giving you both an easy and face-saving way out of that situation.
Or, you became aware of the agitation and interrupted it. The CO2 was a placebo. You have invested already in the idea, it all clicked in your mind.
I'm not sure this is a helpful comment. This is a common story with many medications, where someone notices their feelings are off and suddenly remembers that there is a probable root cause. It's why medications list side effects.
Your comment actually has me convinced that this isn't an issue. I've been a recirculation dude for my entire life, I literally don't drive any other way.
Relevant video of someone experimenting with a CO2 monitor in a car: https://youtu.be/hr9w-ZixAqc
Buildup of CO2 and reduction in O2 are two different effects. We're not in danger of running out of O2 in any everyday situation.
Yeah, I measured over 5000ppm in a taxi with two passengers. Showed the driver how to enable air intake (he didn’t know about the feature) and tried to explain this is deadly. Pretty sure this is commonplace globally.
Generally it’s a miracle to me so many people survive traffic on public roads, statistically.
Cars are not sufficiently sealed for that to make any kind of a difference.
Try it yourself. They really are
Cars aren't hermetically sealed vessel. This is hilarious.
You think that’s stopping CO2 buildup?
Lol yes
Don't forget too, if the CO2 is 1000 ppm, then half of the air in each breath you inhale was recently exhaled by someone else. Yes, airborne viruses are still spreading. I still wear an N95 mask whenever I'm in an indoor space with other people outside of home.
IKEA now has a remarkably cheap ($35) air quality monitor that measures CO2 as well as PM:
https://www.ikea.com/us/en/p/alpstuga-air-quality-sensor-sma...
I don't have one yet but plan to pick one up soon. A CO2 sensor alone from Adafruit is $50+, though that one is more precise. I bought it a while ago and it's still sitting in my todo bin.
I do not give a damm about masks, but yet another reason to prefer work from home.
Flu and other air transmited diseases should be treated as a workplace injury, with proper compensation!
Would that not induce a responsibility to take reasonable preventative measures like wearing masks?
Maybe, but masks do not work. You have to replace it every 30 minutes to preserve filtering capabilities And most germs transfer over touch.
I want this implemented to fullest, preferably with full hazmat suit. Yet more reasons to support work from home.
I haven't heard that 30 minute figure before, you have a reference? I've seen articles about medical workers using masks for much longer.
Installing air filtration and UVC in classrooms and meeting rooms certainly helps.
Since the mask shortage cleared up, HCW have been advised to stop re-using them. I re-use mind til they get dirty, but maybe I should replace them more often.
https://apnews.com/article/fda-n95-masks-plentiful-should-no... (2021)
2021 reddit thread: https://old.reddit.com/r/Masks4All/comments/lhnj10/one_of_th...
Condensation of moisture from breath...
Doing that all the time might not be the best idea for your immune system and neither for the respiratory one too.
The first needs to occasionally see new threats to stay up to date and healthy. The second will not like the constantly restricted airflow.
could you observe an effect on your health after starting to wear the mask? like sickness days per year?
I've noticed that cooking with gas is easily the worst thing for CO2 levels. Even with lots of ventilation my kitchen will hover around 1200ppm until it's over with.
I swear I can feel the 430ppm already. I was born into a world with 340ppm. I can't imagine what it's going to be like when we hit 500+ globally.
I'm in the market for an active CO2 scrubbing solution that I could deploy at home. Scrubbing the entire planet won't work but I could make a small room feel like 1960 again.
I swear I can feel the 430ppm already. I was born into a world with 340ppm.
You’re probably about my age, then, and I’m old. It might not be the baseline CO2 levels. :-)
Kidding aside, that would be hard thing to baseline.
Controlling indoor CO2 is important, but it's a proxy metric for the escalation in indoor bioeffluent VOCs which are a tiring subset of total VOCs. This is why scrubbing indoor CO2 will by itself never produce the pro-cognitive result you want. See https://www.aivc.org/resource/effects-carbon-dioxide-and-wit...
Also, when you cook on a gas stove, it produces numerous other toxic gases which too are critical to ventilate before they even escalate, failing which the lung cancer is risked.
Scrubbing indoor CO2 is sensible only when you want to go below the outdoor CO2 level, not at levels above it.
What have you found so far?
I do feel impaired around 1000ppm. I get headaches. At home I got a few Air Gradient Ones (no affiliation, but they are great) and connected those to my Home Assistant to turn up the ventilation in stages (above 650ppm go up, above 800ppm again, at 1000ppm max). I also do this for the bedrooms, cause in the night it goes up too.
The article talks about "within the hour". With four people in my living room doing normal things it jumps within 20min to around 1000ppm. If I am wrestling with my kids much sooner.
In offices companies often neglect it.
edit: if you are cooking on gas it also has an immediate effect on co2 of course apart from other small particles
People don't understand ppm like they do temperature units. These rebreathed stickers can help drive home the point. Especially when the next respiratory virus season rolls around. https://naltic.com/product/aranet4-rebreathed-percentage-sti...
You will take ~ 1000 breaths per meeting hour. really gross!
This article is rated 100% on my AI smell meter, making it less trustworthy despite convincing arguments.
For instance, I'm now really only sure that author measured a 2000 ppm CO2 in a meeting room once. Everything else could just be LLM trying to invent convincing argument.
Glad someone else is saying it. It has that exact LLM cadence to it, horrible.
The worst thing is, I'm pretty sure humans are starting to mimic that cadence too...
Yeah, I clocked it as AI the moment I read "Here is the uncomfortable part". Pangram detects it as 100% AI-generated:
https://www.pangram.com/history/c410d4b4-abfd-4ca0-b52d-db0d...
Not gonna happen in Germany. I don’t think I‘ve ever seen a windowless room here and it’s common to open all windows at once for a few minutes, just to replace as much air as possible:
Stoßlüften.
Take a look at indoorco2map.com and you will find plenty of places in Germany with bad air measured in a crowd data collection effort. Most notably doctor‘s offices are often very bad. Many supermarkets too. Schools are not well measurable this way but academic research shows they often are at 2000-3000 ppm or even higher. (Disclaimer: I built the website/App)
when i read the article i thought that maybe this is where german ingenuity comes from.
but then germany hasn't been doing so well lately, and people who do most of their work outside should also be doing better...
I noticed this effect really strongly at university. There was one particular lecture hall that was effectively buried in the side of a hill; I can't count how many times I had an early afternoon lecture in there (so it had been in use since 8am), where I just could not focus or stay awake. Assuming sleep deprivation was the problem, afterwards I'd head out and lie down on a bench to take a nap, only to find myself wide awake. I have no trouble taking cat-naps when I'm actually tired, leading me to eventually conclude it was CO2 / O2 in the room that was the culprit.
“That number matters more than it looks.”, then the next paragraph starts with “Here is the uncomfortable part”, and then I closed the tab.
That article's message is spot on.
If your CO2 levels are that high then you should fix the HVAC system and get it up to code or lobby for fixing the code. In many countries, a full air exchange in any office space every X hours is mandatory. In other countries that's optional and they need to get their act together.
In most of the world outside of the US, having "an HVAC system" is extremely rare.
Or just open the window for the world that doesn't have HVAC
A lot of CO2 is bad for thinking.
CO2 is just a tip as office or home is toxic environment anyway. Plastic (e.g. carpets), formaldehyde in furniture, air fresheners… add home office and cooking at home (-> small carcinogenic particles)…
If you start reading How not to die by Michael Greger, you find out that dust, soda and sitting - not CO2 - are real killers…
It's similar to how people think sharks and airplanes are the biggest killers - when in reality it is coconuts, mosquitoes, and motorcycles.
How do you avoid/reduce exposure to dust? Genuine question
Air filters, decluttering, regular deep cleaning, replacing dust-friendly surfaces and furniture (such as carpet, drapes, and upholstered sofas) with things like wood, vinyl, or leather. HVAC maintenance, cleaning, and filters. Washable allergen covers for things like pillows and mattresses.
HEPA-filter air purifier and a robot vacuum that is scheduled to run while your are not in the apartment (to reduce baseline dust) are probably the most simple/cost-effective measures.
Use an air purifier, wear a respirator outside if you live in a polluted place.
Air purifier is good for PM2.5 and other microscopic pollutants but it doesn’t do that much for dust unless it’s particularly light dust and very close to the purifier.
Dust is much more likely to just settle on the ground and be kicked back up than it is to move all the way to the purifier to get stuck in the filter.
I have an air purifier with built in particulate sensor. It doesn't provide numbers, but has a multi-color LED indicator to report PM2.5 level as good/mediocre/bad/terrible. Running a vacuum cleaner that supposedly has a good filter consistently increases the reported PM2.5 level from the first band to the second. The air purifier (or faster/cheaper depending on the weather, just open some windows) can bring it back down again.
Indoor air quality improvements were one of my “pandemic sourdough” activities.
After testing a variety of AQI sensors, I ended up acquiring multiple Airthings-branded devices.
They provided the best mix of CO2/VOCs/PM sensors in a single device with a decent enough app.
There may be better options now, but I have these at both home and office.
Highly recommend doing the research and learning about the environments you’re in, especially if you have little ones at home.
Edit to add: opening windows is usually the easiest/best solution!
Can someone provide an explanation why CO2 concentrations above 1000 ppm have such a negative influence given the fact that CO2 concentration in lungs (at rest) never falls below 10000 ppm?
It simply makes the baseline higher. If you want to go to extreme cases, check carbogen
https://en.wikipedia.org/wiki/Carbogen
I'm not a doctor, but I would consider it in terms of flow and throughput, rather than,—metaphorically—the amount of water the pipe can hold.
Per Wikipedia, at rest 500 ml of inhaled air is diluted with ≥2500 ml [1] of residual air in lungs containing ≥40000 ppm (4%) of CO2 [2]. Other things being equal, increasing concentration of CO2 in ambient air 10x (500ppm -> 5000 ppm) would increase concentration of CO2 in the lungs after taking the breath by less than 2.5% [3].
I imagine it could easily be compensated by an equivalently minor increase of breathing rate or breathing depth.
[1] https://en.wikipedia.org/wiki/Gas_exchange#Alveolar_air
[2] https://en.wikipedia.org/wiki/Breathing#Composition
[3] 5/6 × 40000 ppm + 1/6 × 500 ppm = 33417 ppm; 5/6 × 40000 ppm + 1/6 × 5000 ppm = 34167 ppm; 34167 / 33417 = 1.0225
Ugo Bardi has an interesting take on CO2 and intelligence: https://senecaeffect.substack.com/p/a-new-interpretation-of-...
> Then, somewhere in the second hour, the room quietly gets worse at making them.
Maybe it's not just the air but also the multi-hour meetings that drive people to a sense of "oh god let this finally end now", which leads do decisions that fall short.
A reasonably popular brand's product that uses an NDIR sensor revealed to me just how much the CO2 level increases each night in my two bedrooms.
One of them seems to have much worse ventilation to the extent that it reaches double the level. Opening the window slightly 24/7 keeps it low.
My fiance's chronic headaches/migraines/idk became noticeably less frequent after this change and when they do occur it's usually because the window was accidentally left closed.
Anybody who struggles with this kind of thing might want to try checking their levels. Or just open a window I guess?
Does it work the other way around? Does breathing air with 0% CO2 improve human cognitive performance? I haven't been able to find any research on the effects of lower CO2 concentrations.
Very interesting. It would be nice if HVAC monitored this and helped adjust for optimum performance.
I heard a Freakonomics podcast recently with similar takeaways - that air pollution has a direct effect on cognition skills.
At a career fair in an auditorium I was showing a sensor suite with OLED displaying current readings, one of which was the SCD41 CO2 sensor (they cost more than the esp32!)
I watched the sensor rise from 800 to 1700 PPM by the time the last group left the
It’s quite easy to build one and deploy with esphome and breadboard with stuff you can order on Amazon and have an LLM walk your through hardware and setup.
It is interesting where the rate of speech quickens as the co2 rises and the body starts to notice the co2, or maybe that was just the coffee.
At some point I worked with a team of ~10 people, and we did sprint plannings in 20sq meters room from 10am to 5pm. It was like everyone was high
A bit OT, but was anyone else amazed by the bad UX of that CO2 monitor in the picture?
If you notice, that monitor has a "traffic light" gauge at the bottom to tell you if the current CO2 level is critical. That traffic light is currently showing RED, i.e. highly critical.
The thing is essentially sounding the alarm and prompting immediate action. However, became the traffic light colors are printed on and static and the only dynamic indicator is a small e-paper bit above the color gauge, the effect gets lost completely.
These CO2 monitors have a configurable audio alarm. The present model uses an e-ink display to conserve battery. Physical LEDs would also work, but really in practice you don’t look at the unit and instead are notified by the audio alarm.
Ah, that makes more sense.
For the DIYers, it's simple to get an SCD4x sensor and hook it to a pi, arduino, ESP32 etc (then use CC to create a live web interface). I did this after trying an Inkbird CO2 monitor, which gets reasonable scores in reviews and wanting a live web report in the office.
Interestingly the Inkbird and the SCD4X quite often diverge by anything up to hundreds of PPMs; I kind of back the SCD4x (on a Pi in my case) for accuracy after lots of experimentation, reading the datasheet and ensuring the correct calibration procedurs are followed (basically expose the sensors to outside air once a week).
It's also interesting how much it varies day to day in my one-person office - possibly down to how windy it is outside, even with windows closed one day it never goes about 800ppm, other days it'll hit 1500ppm by lunchtime if I don't open a window.
N.B. Quite possible the Inkbird uses an SCD4x internally, seems reasonable kit so I have no explanation for the differences in readings.
You can also get the IKEA one which uses a good sensor
https://www.ikea.com/au/en/p/alpstuga-air-quality-sensor-sma...
> Open a window.
In most office buildings (towers) that's impossible. You have to deal with what the A/C gives you.
Get a sensor with NDIR system and it should be good. I myself have felt cognitive functions decline during my remote work sessions at home. I have smaller room that gets filled with CO2 when my family visit the room.
Comprehensive AIR monitor system is must to get most efficient output. Author is right here!
i literally had a co2 sensor for my engineering team last fall cause the space was so poorly ventilated. just measuring it continuously radically changed how everyone approached using the space packing wise and ventilation. smelled better too :p
I tend to agree with this observation. I started taking my evening calls (6:30 to 10:30 PM everyday) from my terrace in open air and my overall fatigue became quite less and I feel quite less tired compared to earlier time when I used to take these calls from my room.
LLM prose really sucks the air out of a room.
I remember some years ago after coming from work at 6 pm I was dead tired at home thinking it was due to hard work during the day. Then one summer day decided to code side projects on my balcony and I was building until midnight full of energy.
Goes a long way to prove that industrial air conditioning is absolutely abysmal. If air conditioning actually worked satisfactorily, opening a window should never be necessary unless you want the cold waft of air, while the air conditioning actually delivered high-quality, low-CO2 air without smell. Instead any room at > 20% capacity is quickly filled with CO2 and the putrid smell of bad mouth and body odour. I get it that perfect ventilation would be way more expensive, but at the current level it is just bad, and the windows are sealed shut. It does not make sense from a human perspective.
Working from home next to my open window feels generally way better then being in the office. Perhaps this is contributing. Still, seems more of a case for WFH rather than against, as article mentions some people have tried to make the case for.
I have a CO2 monitor and I don't understand one thing - it seems that CO2 increases more quickly during summer than during winter. If I close my windows it takes longer to reach 1000 ppm during winter than it does during the summer.
I didn't gather concrete data on this but this is just what I eyeballed over the last few years. Does anyone know why could this be the case?
Do you have a forced-air heating system?
Great article! I did build a open source one years ago: https://andrefiedler.de/open-source-co2-ampel/
It's on my desk and I can confirm, opening the window if it gets orange helps a lot with thinking.
Some days in the morning it shows red and I barely can't think or get awake. Opening the window and it changes instantly.
I find it kind of funny that we've been low-key suffocating the higher order function of our brains ever since we started building structures to live in with very little awareness of it. My mom is one of those people who complains that the air is getting stale and opens a window, the hero we needed.
Not that we need more anecdotal evidence but I’ve long felt a certain restlessness and inability to think creatively somewhere in the early afternoon. I work from home with my wife. I’ve eliminated lunch, coffee, and a ton of other variables. The one variable that finally had a distinct effect to my mental state was opening a window.
I wonder if the corona times trend to WFH and jump to Teams/Zoom/etc meetings instead of physical meetings had/has a positive effect in regards to this.
Why did your startup fail? The CO2 was sitting at 1.000 ppm
I also use my Aranet everywhere. The nice thing is you quickly develop a feel for when you need to ventilate spaces you know so you don’t need it there anymore. I also developed a feeling for new (to me) rooms a bit.
I once woke up with the fam in a hotel with airco at 5500 ppm. It is then that I learned the airco does not blow fresh air (logical after thinking about it).
As a cyclist, I've heard a similar argument for years about indoor training, and particularly doing difficult indoor intervals beyond FTP.
My employer started using CO2 monitors in meeting rooms 15 years ago, it’s really a useful thing to have. As well as the meeting rooms having windows you can open.
I wonder how many high impact political decisions (eg EU treaties) have been made in rooms like these.
Hey, just FYI to everyone:
Even though this article is conveying good (and useful) information, it seems to be completely AI-generated.
Pangram clocks it as 100% AI: https://www.pangram.com/history/c410d4b4-abfd-4ca0-b52d-db0d...
Someone else in the thread lists it as 99%: https://www.salahadawi.com/hacker-news-ai-detector
Also, it sort of jumps out at you if you're used to reading AI writing. Claude loves to start paragraphs with "Here is the uncomfortable part".
I'm not necessarily saying this automatically makes it bad, but everyone should be aware of the source of their information.
One easy way to fix this for many people's bedrooms or home offices: look at your HVAC system, and there's probably an option to have the fan run all the time, even if the heat or air isn't running. Turn that on, and your home's CO2 levels will drop substantially.
Topic must be very interesting to have this much discussion on an obviously AI-written article. I couldn’t get past the first few sentences.
Matches my experience. Basement home offices are the worst offenders.
Interesting.
Perhaps using non-ozone negative ionizers would also help.
The practical bottleneck for most AI tooling isn't model capability anymore - it's the orchestration layer. Getting reliable behavior across edge cases requires more engineering than people expect from demos.
Is this a bot?
I can feel the AI in the text.
Yeah, I noticed it at "Here is the uncomfortable part. 1,000 ppm is not an extreme number."
Either AI, or LinkedIn brainrot.
Are there studies which analyze performance Vs artificial CO2?
Natural CO2 in a room probably correlates strongly with other things given off by humans... Farts, water vapour, viruses, etc.
The effect needs to be properly understood before totally redesigning the nations ventilation systems on a possibly wrong premise.
There are. The article literally cites a publication describing just such a study.
The really uncomfortable part is that 1000 ppm isn’t that far off from how EARTH will be. A terrifying scenario that will be like Total Recall with people clamoring for and paying for fresh air. Those that can’t will be permanently in a stupor.
https://science.nasa.gov/earth/explore/earth-indicators/carb...
The building science community has not buy and large came to the agreement that the CO2 itself is the cause of the cognitive decline. It could be the Canary in the coal mine telling us there is an accumulation of compounds causing the decline.
Why that matters? You need good ventilation regardless, but instead of just thinking of CO2, try to minimize compounds in your air by selecting things for the room that smell less and off-gas less.
Similar to this a closed motorcycle helmet without air circulation increases CO2 extremely rapidly, within 60s it's already at really high levels. Open your visor when you stop!
Buying one of these gadgets killed my brain fog
i love seeing things i saw on twitter two years ago at the front page of hn man like what are we doing
if price is no object get the AirGradient PM2.5+CO2
but Ikea now makes the most affordable PM2.5+CO2 sensor, at $35 a no-brainer
https://www.ikea.com/us/en/p/alpstuga-air-quality-sensor-sma...
in there is a very nice/expensive Sensirion SN63C sensor that costs nearly as much as the Ikea itself
https://sensirion.com/company/news/press-releases-and-news/a...
unfortunately Ikea requires Matter network not plain wifi for communication so I've been looking for a cheap Matter hub or DIY SPR
if I travel and expect to be working I now bring a CO2 meter
I am able to open the windows at home and at work but have to be reminded to air out, but I always feel much clearer when I do.
Also, take walks. I am lucky to be able to walk to and from work and it helps immensely.
Just open the door
You know what also impacts my decision making ability? Freezing my ass off because people are opening all the windows every five minutes.
Wow, what a revelation. People rediscover basic things in life :D.
open a window, wait, ok, ok, turn up the , wait, no, ummm, hmmmmm re, re, no forget that, hmmm anyway, as a person with a strong interest in civil engineering, systems, and the subset of air handling, I can say that there has long been disenting arguments about how things are built,that have been ignored due to cost, which are large in terms of internal volumes required, and the intractable issues around, noise, filtration, heating/cooling and maintenance. And as the climate warms, and in many areas pollution increases , the inadequate methods used to "calculate" requirements, get further from real world needs. You could try throwing a desk through a window, but as that is one of the things the planners and engineers have antisipated, it will prove to be surprisingly difficult.
Aranet detectors are superb, and – best of all! – made in Latvia.
Support European!
https://aranet.com/en/home
Yet another reason to have meetings while walking outside: air quality and a natural limit on time, and the mental benefits that come from movement.
Requires an area around your office that isn't ugly or overrun with cars.
It needs to be safe (including from pollution), but you could absolutely just walk around the parking lot.
Scandinavia wins again :)
requires that everyone is comfortable walking and has no physical impairments.
Not to talk about the weather either.
> You gather your most expensive people into a room to make your most important decisions.
A terrible way to make decisions.
What should be a better way?
Make them mostly async, bringly only the very pointy details that need nutting down sync. If knowledge transfer is needed in a meeting that could be done seperately.
Put it this way do you need to book a 3h meeting with your spouse to decide if to buy a house? Nope all the research and decision criteria were in advance. That final minute of making the decision is a cross check over that work.