I bought a cheap CO2 meter that actually measured TVOC (or something else) and infered the CO2 from it. Didn't like it. Many things would case false positives:

I bought a cheap CO2 meter that actually measured TVOC (or something else) and infered the CO2 from it. Didn't like it. Many things would case false positives: farting, cleaning something with alcohol, steaming food, etc. And it had no option to disable the buzzer which would beep loudly for minutes. Cheap CO2 meter didn't fix anything and created a noise pollution problem.