alt Hacker News> In the first year of the COVID-19 pandemic I learned that we can estimate our level of risk by checking the concentration of carbon dioxide in the air, because when infected people breathe out virus aerosols, they also breathe out CO2.
The above is from the author early on. So they go out of their way to point out that it is an estimate and also point out the mechanism that allows it work as an estimate in some conditions. "when infected people breathe out virus aerosols, they also breathe out CO2."
The article does not reenforce this through out the article though and leaves it to the reader to keep in mind.
The previous post is essentially the background on this topic: https://grieve-smith.com/ftn/2026/02/so-you-want-to-monitor-...
> Why carbon dioxide? Because everyone who exhales COVID (or flu, or RSV) aerosols also exhales carbon dioxide, and good ventilation removes both disease aerosols and CO2. Under many conditions, the concentration of CO2 particles in a space can give us an idea of how much risk there is of catching or passing on a respiratory disease.
> Unfortunately, the relationship between the numbers on a carbon dioxide monitor and the disease risk is complicated, so there are some things to know if you want to do your own monitoring.