Can COVID-19 spread through air conditioning?

In a study published last April in the Emerging Infectious Disease Journal, researchers reviewed the spread of COVID-19 at a diner in Wuhan, China. The study found that one asymptomatic person sitting beside an air conditioning unit at a diner resulted in nine other people becoming infected.

“Now could an air conditioner have blown droplets from one person to another? It’s possible,” says Dr. Chakrabarti, an infectious disease specialist in Mississauga, ON. “We also have to remember, at that time when the study was done, Wuhan was in the grips of this major outbreak. So even outside of the restaurant, people had a huge amount of opportunity to get the virus. So that’s something to think about.”

Research teams at the University of Alberta analyzed this same study out of Wuhan and it sparked a research project. A team led by Dr. Lexuan Zhong is working diligently to determine if updating the design of HVAC systems could reduce the risks of airborne transmission within a confined space?

“We are exploring HVAC design and operation features that can affect virus transmission, such as ventilation modes, air distribution patterns, recirculation ratio, filtration, advanced air cleaning technologies,” explains Zhong.

The work in Alberta started in March 2020 and is expected to continue through 2022. Zhong says the end goal would be to “provide direct guidelines to building operators and policymakers.”

Researchers at the University of California published a report at the beginning of this pandemic reporting that air inside a built environment, such as homes, offices, and buildings, needs to be exchanged. In other words, researchers recommended people open their windows so that it could potentially disperse contaminated air inside of a building.

Collective research today tells us there is a possible risk that an AC unit could circulate COVID-19. However, there is very little proof that it has happened or is the direct cause of the spread.

“One thing that is for sure, is being in an indoor environment, especially with poor ventilation for a prolonged period of time, is the main way that people get infected,” Dr. Chakrabarti explains. “For example, in an old building where the air circulation is poor - that stale air will stay there while you are talking, coughing, clearing your throat - and then all those droplets can then easily spread to the next person increasing the risk of infection.”

Droplet transmission still stands as the main way people can contract COVID-19, according to the World Health Organization. This is why physical distancing, hand-washing and restrictions on social gatherings are still extremely important.