(2021-02-17) The Coronavirus Is Airborne: Here's How To Know If You're Breathing Other People's Breath

The coronavirus is airborne. Here’s how to know if you’re breathing other people’s breath. Crandall’s restaurant is open again — with a CO2 monitor that displays a reading he tries to keep under 450 parts per million, only slightly higher than levels in the outside air, per state policy. Thanks to the human burning of fossil fuels, outdoor levels currently average about 415 parts per million, and are steadily rising.

one popular model, the $250 Aranet4, sold out rapidly

The trend is also catching on fast with a number of coronavirus activists — or citizen scientists — who tweet out their readings in different locations and use the hashtag #covidco2

Marr is a medical adviser to the network of CrossFit gyms — installing indoor monitors is now part of their coronavirus guidelines, at her urging.

some worry about misunderstandings

Experts recommend devices that use a technology called non-dispersive infrared sensing (NDIR)

*he has calculated that when the indoor concentration of carbon dioxide reaches 800 parts per million, then each time you breathe in, one percent of the air you inhale has come from the exhalations of others. During a pandemic, that’s an alarming thought.

But carbon dioxide concentrations of 1,000, 2,000, or even 4,000 can be found in poorly ventilated indoor spaces, where people simply aren’t aware how much of the gas has built up.*

many readings will fall into more of a gray area, somewhere between about 700 and 1000 parts per million.

Are you safe in such a space? The answer is, it depends. For instance, Corsi notes, a space with 25 people in it and a CO2 measurement of 700 parts per million is far better ventilated than one with three people in it and the same measurement.

if a room has a portable HEPA air filter, or a good HVAC system with similarly strong filters (properly installed), then your risk will be lower even though carbon dioxide levels may seem a tad high. Carbon dioxide, a tiny molecule, passes right through these filters, even though the larger aerosols containing viruses can be caught by them.

Ideally, he thinks, there should be an app that would help people interpret CO2 levels by inputting other information, such as the number of people in a space and how much time they plan on spending there.