It's a bit tricky, because one of the most expensive parts of an air quality meter appears to be the CO2 sensor. Less expensive sensors approximate CO2 concentr

It's a bit tricky, because one of the most expensive parts of an air quality meter appears to be the CO2 sensor. Less expensive sensors approximate CO2 concentration (it's referred to as "eCO2") and can be wildly off due to the way they sense gas concentrations. If you have the equipment to make electronics at home and are willing to DIY, it can be done for less than $100 and will be comparable to an off the shelf unit.