Personal air quality

The next health frontier will be personal air quality; what are you breathing? The best measurable proxy we have right now is the level of CO2 in the air. The more CO2 present, the more likely it is full of the exhalations of others, and the greater chance of infectious agents. The small, lightest CO2 monitor is AirSpot ($144), which is smaller than the size of a thumb drive, and will give you instant CO2 levels. I carry it in my pocket when travelling; if the levels get high, I can choose to mask, or exit if possible. (The highest level I’ve seen so far is in the waiting room at the DMV.) — KK