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.”
