The impetus for measuring carbon dioxide is simple: An increasingly powerful body of evidence suggests the coronavirus is airborne, capable of traveling distances well beyond six feet in tiny aerosols released when infected people talk, shout, sing or just breathe. But there’s currently no sensor that can monitor, in real time, whether these infectious aerosols are floating around us when we’re indoors.
But carbon dioxide can, in some ways, act as a proxy. People exhale it when they breathe, and the gas builds up in indoor spaces that aren’t well ventilated, reaching concentrations far above the baseline level of outside air.
“It gives you some insight into ventilation, which is really hard to figure out otherwise,” explains Linsey Marr, an aerosol expert at Virginia Tech. “Even building owners and managers often don’t know much about the ventilation. The person who knows is the person who installed it, and they are usually long gone.”
Marr is a medical adviser to the network of CrossFit gyms — installing indoor monitors is now part of their coronavirus guidelines, at her urging.