Fresh Indoor Air? A CU Boulder Aerosol Expert Suggests Measuring CO2

Feb 23, 2021

The Centers for Disease Control has said proper ventilation in indoor settings can cut down the spread of COVID-19. But how can you tell whether a space is in fact well ventilated?

Jose-Luis Jimenez is an aerosol expert at the University of Colorado Boulder. Ideally, he said, a device would exist that beeps when it detects COVID-19 particles in the air. But we're not there yet. In the meantime, he says a carbon dioxide monitor can serve as a proxy.

"One thing that we have found that's practical, that can be done with limited costs, and that is very useful, is to measure CO2," Jimenez said.

We breathe out CO2 when we exhale. So knowing how much CO2 is in an indoor space can give us a sense for how much air we're inhaling from other people's respiratory systems.

Outdoor carbon dioxide levels are currently about 415 parts per million. Levels in restaurants, classrooms, offices and other indoor spaces often exceed 1,000 ppm.

"We recommend that we keep all indoor spaces when we share the air below 700 parts per million," Jimenez said.

For around $100 at the low end, a carbon dioxide monitoring device can indicate how much fresh air is circulating. Jimenez said measuring CO2 levels in indoor spaces is already common practice in places like Taiwan and South Korea.

"So these countries are definitely ahead of the U.S., and we should try to catch up," he said.

Jimenez argued that the federal government's emphasis on ventilation, and on indoor air quality in general, should remain long after the pandemic is over.

This story was produced by the Mountain West News Bureau, a collaboration between Wyoming Public Media, Boise State Public Radio in Idaho, KUNR in Nevada, the O'Connor Center for the Rocky Mountain West in Montana, KUNC in Colorado, KUNM in New Mexico, with support from affiliate stations across the region. Funding for the Mountain West News Bureau is provided in part by the Corporation for Public Broadcasting.