Which ones did you get? I've been thinking along similar lines recently, but they are somewhat expensive and it's hard to say which ones are even legit.

So far the MH-Z19 modules are on the top of my list for pairing with an ESP or something and logging data to NAS but I've yet to order any.

Senseair S8 paired with ESP-32 has served me well over the past 3 years, but they have to be exposed to outside air at least once a week or so. Otherwise they quickly lose their zero point and start reporting thousands of PPM as mere hundreds.

I think other models with auto-recalibration also suffer from this (including MH-Z19). It's probably not a problem for you, but if you too live in an extremely polluted area and have to keep your windows shut for weeks at a time, it might be.

interesting

I got the Netatmo Smart Indoor Air Quality Monitors. They are somewhat expensive, but I got a good deal, 69 EUR a piece. They also monitor temperature, air humidity and noise levels.

Airthings, expensive but just does the job perfectly.

I’m quite happy with Qingping Lite. Doubles as a clock, PM10, charges via USB-C.

I recently bought one expecting to see something interesting and it mostly just stays stable all day, even with the door closed. Maybe my house has good ventilation.

In my case I have exceptionally drafty windows. The rooms with new windows all have CO2 elevate almost linearly with time human is in room.

Stays stable at 400ppm or 1500ppm?

365ppm atm

That's low. Does that means you're at a higher elevation than I am at near-sea-level?

1500ppm isn't great, but "drunk" is hyperbole.

It might make you feel different - and maybe not great for being productive, but it would be hard to notice.

That's less than half of what they keep the ISS at, BTW.

wow, you are right. Then again, I suspect they're challenged to keep it low given the space. Seems astronauts report headaches more above that level.

I’m honestly just a huge skeptic about indoor CO2 levels. OSHA says 5000 ppm is a safe upper limit, and nuclear submarines operate at pretty high levels too. I strongly suspect this is just one of those weird social media health crazes.

How did it actually improve things?

I know now when I have to open the window and let the air in, and consequently I feel less tired and have more energy.

Did your home have poor ventilation? I don't know if I need to worry about this as each of my rooms has (modern I think) vents.

My dad had a balanced heat recovery ventilation installed few years ago. I think it might be undersized a bit as it’s somewhat loud when running at 100%. He doesn’t like the noise so he runs it at 40% or so.

After getting meter I found it’s def not enough, especially in rooms with more people doing some activity. He still doesn’t believe my meter is accurate tho.

I thought our ventalation was fine. Then we got at CO2 sensor for covid related reasons. When we replaced our 30 year old windows the numbers went through the roof.

We updated our air exchanger to fix the problem. Venmar and Vanee are two big brands in america.

I live in Germany, and here the houses generally don't have machine ventilation so one has to air manually and regularly. As an example: earlier today I closed the door to my office (ca. 18 m2 / 194 sqft). The window was closed. After 2 hours the CO2 levels rose from 935 ppm to 1966 ppm. Letting air in for 20 minutes reduced the CO2 levels to 869 ppm.

The trick is to have two windows open so there is a pressure gradient that creates circulation with the air outside.

You can get it down to 400ppm even with people in the apt.

In a room with poor ventilation it can go to several percent.

It is inert -- but your brain prefers oxygen to CO2, despite oxygen being far from inert.