A first pass at that would be a CO2 dosimeter. Because humans breathe out CO2, and if the ventilation in the area is poor relative to the number of humans insi

A first pass at that would be a CO2 dosimeter. Because humans breathe out CO2, and if the ventilation in the area is poor relative to the number of humans inside of it, then you will get a higher concentration of CO2, and thus you would also be more likely to have a higher concentration of viruses and other substances that can be airborne. Just because you have high CO2 doesn’t necessarily mean that you have high concentrations of the virus particles that could cause a COVID infection, but there is a high correlation, and high CO2 is bad for you in plenty of other ways as well. So, yes please — give me a cheap, portable, badge-like way of measuring my exposure to high levels of CO2!