The bottleneck might be the air in the room • Hacker News Board

Re: The bottleneck might be the air in the room

#121

Post by microtonal » Sat, Jul 04, 2026, 9:34 AM UTC

bjackman wrote: post #103

microtonal wrote: post #85

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 a…

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.

Re: The bottleneck might be the air in the room

#122

Post by swe_dima » Sat, Jul 04, 2026, 9:34 AM UTC

if I travel and expect to be working I now bring a CO2 meter

Re: The bottleneck might be the air in the room

#123

Post by nnevod » Sat, Jul 04, 2026, 9:34 AM UTC

progval wrote: post #75

p-e-w wrote: post #57

Earlier quoted context omitted.

> 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…

>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.

Re: The bottleneck might be the air in the room

#124

Post by nok22kon » Sat, Jul 04, 2026, 9:35 AM UTC

Tossrock wrote: post #12

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...

could be a selection effect at work

Re: The bottleneck might be the air in the room

#125

Post by hypfer » Sat, Jul 04, 2026, 9:35 AM UTC

npunt wrote: post #35

kashishgrover wrote: post #27

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 i…

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.

Re: The bottleneck might be the air in the room

#126

Post by halper » Sat, Jul 04, 2026, 9:37 AM UTC

w-m wrote: post #67

KerrickStaley wrote: post #51

Earlier quoted context omitted.

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 ef…

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?

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.

Re: The bottleneck might be the air in the room

#127

Post by metalman » Sat, Jul 04, 2026, 9:37 AM UTC

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.

Re: The bottleneck might be the air in the room

#128

Post by nok22kon » Sat, Jul 04, 2026, 9:37 AM UTC

microtonal wrote: post #111

nok22kon wrote: post #109

Earlier quoted context omitted.

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.

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

Re: The bottleneck might be the air in the room

#129

Post by inigyou » Sat, Jul 04, 2026, 9:39 AM UTC

deanc wrote: post #92

kashishgrover wrote: post #30

Earlier quoted context omitted.

https://www.youtube.com/watch?v=1Nh_vxpycEA

This is not a peer-reviewed study. It's a Tom Scott youtube video.

Are we not peers to Tom Scott?

Re: The bottleneck might be the air in the room

#130

Post by inigyou » Sat, Jul 04, 2026, 9:41 AM UTC

kashishgrover wrote: post #27

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 i…

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.