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The bottleneck might be the air in the room

537 pointsby gslintoday at 6:32 AM324 commentsview on HN

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tmp147963today at 3:03 PM

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)

gpt5today at 7:13 AM

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.

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dr_dshivtoday at 2:59 PM

Cornelis Drebbel figured out how to manage co2 in 1610 when he deployed the first submarine. With 4 oarsmen submerged in a leaky wooden sub, running out of oxygen was an issue — as was excess co2. Somehow they were able to stay for hours at a time.

Boyle describes Drebbel’s use of a “chymical liquor” to refresh the air. Father of CO2 reduction tech right there, haha.

https://sourcelibrary.org/book/philosophical-works-vol-2-boy...

Fwiw, I think he used about 70kg of lime as a ballast.

vertnerdtoday at 11:01 AM

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.

deanctoday at 7:25 AM

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.

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Tossrocktoday at 7:22 AM

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...

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microtonaltoday at 8:58 AM

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/

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kashishgrovertoday at 7:40 AM

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.

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chrisweeklytoday at 1:05 PM

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.

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oasisbobtoday at 7:36 AM

There needs to be a meter for the amount of AI writing in blogposts. Same physics, same climb, same afternoon fog.

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bob1029today at 12:10 PM

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.

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smooctoday at 10:29 AM

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

Aperockytoday at 8:51 AM

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.

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throwaway81523today at 7:14 AM

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.

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teiferertoday at 12:25 PM

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.

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gwdtoday at 8:41 AM

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.

hanspageltoday at 8:45 AM

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.

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rikschenninktoday at 7:48 AM

“That number matters more than it looks.”, then the next paragraph starts with “Here is the uncomfortable part”, and then I closed the tab.

sixtyjtoday at 7:28 AM

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.

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jumploopstoday at 9:49 AM

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!

eitau_1today at 8:11 AM

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?

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Beijingertoday at 12:28 PM

Ugo Bardi has an interesting take on CO2 and intelligence: https://senecaeffect.substack.com/p/a-new-interpretation-of-...

ncrmrotoday at 12:26 PM

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.

machined_graytoday at 1:15 PM

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!

xg15today at 12:04 PM

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.

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_deftoday at 7:32 AM

> 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.

sohpeatoday at 8:24 AM

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?

red75primetoday at 8:34 AM

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.

nenadgtoday at 8:59 AM

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

alienbabytoday at 12:42 PM

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.

carterschonwaldtoday at 10:10 AM

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

zh3today at 8:38 AM

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.

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bambaxtoday at 9:05 AM

> Open a window.

In most office buildings (towers) that's impossible. You have to deal with what the A/C gives you.

zeroptoday at 9:33 AM

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.

Yajirobetoday at 11:16 AM

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?

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lexojtoday at 8:56 AM

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.

materialpointtoday at 9:07 AM

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.

doginasuittoday at 11:17 AM

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.

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SunboXtoday at 10:06 AM

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.

abalashovtoday at 12:41 PM

As a cyclist, I've heard a similar argument for years about indoor training, and particularly doing difficult indoor intervals beyond FTP.

layer8today at 12:14 PM

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.

ccozantoday at 8:51 AM

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.

joshuaS98today at 9:00 AM

Why did your startup fail? The CO2 was sitting at 1.000 ppm

teekerttoday at 9:43 AM

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).

Retr0idtoday at 12:12 PM

LLM prose really sucks the air out of a room.

skrebbeltoday at 9:20 AM

I wonder how many high impact political decisions (eg EU treaties) have been made in rooms like these.

JoshTripletttoday at 8:27 AM

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.

clbrmbrtoday at 12:30 PM

Matches my experience. Basement home offices are the worst offenders.

scrolloptoday at 12:49 PM

Interesting.

Perhaps using non-ozone negative ionizers would also help.

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