As COVID-19 cases surge in southern areas of the United States, some scientists hypothesize an increase of people spending time in air-conditioned spaces could be playing a role in the spike, especially since rates aren’t going down in summer. But it’s worth asking the question: Does air conditioning spread the coronavirus?
According to the Harvard Gazette, Professor Edward Nardell suggested that hot temperatures could be having the same effect cold winters have on viral infection rates. He said the warm weather could drive people to spend more time indoors, where they breathe in recycled air.
“The states that, in June, are already using a lot of air conditioning because of high temperatures are also the places where there’s been greater increases in spread of COVID-19, suggesting more time indoors as temperatures rise,” Nardell said. “The same [thing] happens in wintertime, with more time indoors.”
Nardell’s hypothesis is based on the idea that in some cases, COVID-19 has been spread via airborne transmission—on which the science community still has not come to a consensus. Although the World Health Organization says the research behind the claim is inconclusive, the New York Times reported in early July that 239 scientists sent the WHO a letter supporting the claim.
“As people go indoors in hot weather and the rebreathed air fraction goes up, the risk of infection is quite dramatic,” Nardell said.
Nardell recommends either spending more time outside when possible or increasing ventilation indoors. He also supports germicidal lamps, which have already been proven to prevent the spread of tuberculosis.
However, the research about the effects of air conditioning is inconclusive. Other experts suggest that air conditioning actually helps fight the spread of COVID-19.
William Bahnfleth, chairman of the epidemic task force convened by the American Society of Heating, Refrigerating and Air Conditioning Engineers, told the Washington Post that most A/C units used by American businesses prevent the spread of the virus through ventilation and filtration.
Bahnfleth added that the engineering society is also recommending business owners take steps to mitigate the spread of COVID-19, including the suggestion that they increase the amount of outside air filtered into spaces. Current codes in most states require restaurants to replace all of its air with outdoor air about once every hour. The society is recommending they increase it to three times an hour.
Experts interviewed by Health said that while the risk of infection may be higher inside, they don’t think people should be necessarily fearful of indoor public places—and they definitely shouldn’t turn off the air conditioning.
Instead, people should focus on following the recommended CDC guidelines when venturing outside their homes: Wear a mask, practice social distancing, avoid touching your face, and wash your hands often.