Carbon Dioxide Levels Reflect COVID Risk

Tracking carbon dioxide levels indoors is an inexpensive and powerful way to monitor the risk of people getting COVID-19, according to new research from CIRES and the University of Colorado Boulder.


In any given indoor environment, when excess CO2 levels double, the risk of transmission also roughly doubles, two scientists reported this week in Environmental Science & Technology Letters.

The chemists relied on a simple fact already put to use by other researchers more than a decade ago: Infectious people exhale airborne viruses at the same time as they exhale carbon dioxide. That means CO2 can serve as a “proxy” for the number of viruses in the air.

“You’re never safe indoors sharing air with others, but you can reduce the risk,” said Jose-Luis Jimenez, co-author of the new assessment, a CIRES Fellow and professor of chemistry at the University of Colorado Boulder.

“And CO2 monitoring is really the only low-cost and practical option we have for monitoring,” said Zhe Peng, a CIRES and chemistry researcher and lead author of the new paper. “There is nothing else.”

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