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Can air conditioners spread coronavirus droplets?

Last Updated Aug 10, 2020 at 10:30 am PDT

FILE - A window air conditioning unit in Toronto. (Source: CityNews Toronto)

Study blamed air conditioner at restaurant in China for 10-person outbreak

Risk of HVAC system spreading virus low if it is new and well-maintained

Places without ventilation system should leave doors and windows open

NEWS 1130 is working hard to get you the information you need about the COVID-19 pandemic.

We are responding to your questions in a segment we call NEWS 1130 Gets Answers.


Donna wants to know if air conditioners can spread the novel coronavirus. She heard that HVAC systems can spread respiratory droplets carrying the virus throughout an indoor place and is concerned the warmer summer weather will lead to more infections as more air conditioners are turned on: “If someone in the building is shedding the new coronavirus, it can build up in the recirculated air.”


A study published by the U.S. Centers for Disease Control linked 10 cases of COVID-19 to a windowless, air-conditioned restaurant in Guangzhou, China.

The customers were sitting more than a meter away from the carrier – too far to be infected by the typical spread of respiratory droplets, the researchers found.

“We conclude that in this outbreak, droplet transmission was prompted by air-conditioned ventilation,” they wrote.

But that study doesn’t tell the whole story of the relationship between air conditioning and the spread of the novel coronavirus, according to Karen Bartlett, a UBC professor of occupational and environmental health.

“There’s no evidence that a well-maintained, professional HVAC [heating, ventilation, and air conditioning] system will spread COVID virus,” she said.

Bartlett said a proper ventilation system will actually reduce the risk of COVID-19 spreading by circulating air from inside out and vice versa, as opposed to the air conditioner in the Chinese restaurant, which recirculated indoor air.

Buildings without air conditioning or with outdated systems – including older churches, schools, seniors homes, restaurants and other small businesses – are “way more likely” to host an outbreak, Bartlett said.

“What we need is fresh air supply coming into a building,” she said. “It’s when the air is stagnant, we don’t have that fresh air coming in that the person-to-person spread becomes much more of an issue.”

Bartlett’s advice to anyone managing a space without a high-quality ventilation system: open doors and windows to promote as much ventilation as possible.

The province also urges businesses and public institutions to increase ventilation, as well as installing plexiglass barriers, increasing space between people and encourage the use of masks.

The B.C. Centre for Disease Control also said poor ventilation poses a greater risk than air conditioners.

Spokesperson Jane Campbell said people should avoid using portable air conditioners in unventilated spaces.

“When using air conditioners and fans in ventilated spaces, air should be moved from higher places to lower places whenever possible instead of having strong airflow at breathing height,” she said.

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