> The question after that comes down to calibration and test data. Is there an easy way to create CO2 density and/or PM2.5 particles of a certain density?
Most CO₂ sensors have the ability to calibrate to either 400 ppm or 0 ppm. So if you really care enough, you can fill a small box with nitrogen and calibrate to 0 ppm.
Most CO₂ sensors have the ability to calibrate to either 400 ppm or 0 ppm. So if you really care enough, you can fill a small box with nitrogen and calibrate to 0 ppm.