1/7 Review of low-cost CO2 meter for air-quality monitoring. Summary: useless.
Because of Covid-19, it is recommended to ventilate indoor spaces to keep CO2 concentration below some limit (700 to 1200 ppm depending on which recommendation you follow).
Because of Covid-19, it is recommended to ventilate indoor spaces to keep CO2 concentration below some limit (700 to 1200 ppm depending on which recommendation you follow).
2/ This CO2 meter is available on AliExpress for €15 or in the Netherlands for €33, under various brand names. Name plate: "Model T01". It does respond to something in the air, but most likely not CO2. The displayed values have very little to do with the CO2 concentration.
3/ A simple test. Fill a plastic bag with room air, add a little of your own breath, and look at the numbers. If you mix breath and outdoor air in a 1:20 ratio, it should read around 2500 ppm. Instead, I get around 1000 ppm.
4/ A ziplock bag of thick PE plastic does not leak a significant amount of CO2 within hours. However, this is what it "measures": after 35 minutes, it goes back to 450 ppm. Other containers, metal or plastic: all similar results.
5/ As a physicist, I don't see an explanation of this response that involves a good-faith effort of the maker. The purpose seems to be to show that it responds to CO2-rich breath and show outdoor-air-like values when left alone for a while.
6/ The sensor appears to respond to changes in concentration of various gases without any specificity to CO2: a drop of evaporating alcohol near the device will immediately push the readout value to its max (5000).
7/7 Unfortunately, reliable CO2 meters seem to cost at least €180. Don't buy this product. If you find another cheap meter, you can test it using the same procedure as above.
8/7 P.S. You can build your own device for about €60 in materials (schematics are on the 'net), but you need some tools (configuring Arduino-like devices) and spare time for that.
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