Skip to content

Breaking News


Measuring carbon dioxide in indoor spaces is a good indicator of the risk of becoming infected with coronavirus, according to a new study by University of Colorado Boulder researchers.

The study by researcher Zhe Peng and Professor Jose-Luis Jimenez of the Cooperative Institute for Research in Environmental Sciences builds on previous research to show that when people who are infected with COVID-19 exhale carbon dioxide, they also exhale airborne particles containing coronavirus.

Peng and Jimenez’s research presents a way to prevent the spread of coronavirus without resorting to extreme measures like widespread lockdowns.

“Lockdowns imposed to various extent worldwide for the COVID-19 transmission reduction are not supposed to be long-term measures, otherwise they lead to unaffordable social and economic costs,” the study states. “On the other hand, resumption of social, educational, and business activities raises concerns about transmission resurgence.”

While the study dives into different variables that can be used to determine the exact risk — the number of people in the indoor space, how many people are likely infectious based on local data, the number of immune people, breathing rates — the broad takeaway is that the lower the levels of carbon dioxide in a space, the better.

“The chance of occupants being infectious is pretty much constant at a specific time or indoor space, so the relative risk is pretty much proportional to the carbon dioxide sensor rating minus the outdoor carbon dioxide level,” Peng said. “We call this excess carbon dioxide.”

Measuring carbon dioxide can be applied in a range of settings, Peng said, from coffee shops to hospitals.

But it may be particularly useful in restaurants, when people shed masks to eat and no one knows who might be infectious.

“The higher the carbon dioxide level in a specific indoor space, the higher the infection risk for that space,” Peng said. “It should be very simple for a business owner to act — they simply need to lower the carbon dioxide reading as much as possible.”

And that’s as simple as increasing ventilation, Peng said, like opening doors and windows.

There’s not a hard and fast rule about what level of carbon dioxide makes a space safe from coronavirus, Peng said.

Outdoor carbon dioxide levels are usually at 400 parts per million and it’s best not to be in spaces that exceed 1,000 parts per million. But even then, someone who is in a gym — with people breathing heavily and often — will be at a higher risk than someone sitting in a library.

“But if you can lower the carbon dioxide level as much as possible, it can be much safer than it usually is,” Peng said.

Using carbon dioxide sensors is a good way to measure how well-ventilated an area is, Peng said, and has applications beyond coronavirus. Decreasing carbon dioxide levels in the air by increasing ventilation can help whether it’s making public spaces safer during flu season or clearing out chemical fumes.