Can air conditioning units transfer droplets of COVID-19 throughout your home?

Posted at 6:19 AM, Jul 20, 2020
and last updated 2020-07-20 06:19:27-04

(WXYZ) — Many anticipated or hoped for a drop in COVID-19 cases during the warm summer months, but spikes are being reported across the country – including here in Michigan.

Experts are now taking a look at air conditioning, and whether it plays a role in the transmission of the virus.

"There's some debate right now in the medical community. They think, in general, that droplets are probably the larger source of transmission and that's important because droplets tend to fall to the ground heavier," Dr. MeiLan Han, a pulmonary specialist from Michigan Medicine, said.

Heavier than aerosols, which Han said are smaller particles that hang in the air a little bit longer, and could be carried by air conditioning currents.

"There was actually a study that looked at transmission of virus in China and in particular they looked at who in the restaurant got infected and it looked like it might be in the air conditioner path and that's kind of what I think has raised some of the questions," she added.

"The one thing we know for certainty about disease transmission is that generally, it's more likely indoors for a number of reasons," Penn State Professor Wiliam Bahnfleth said. "One of them is that contaminants that are generated indoors can concentrate."

Bahnfleth chairs the American Society of Heating, Refrigerating and Air Conditioning Engineers task force. He said there are many A/C systems that only heat and cool the inside of a building. Those fail to bring in fresh, outside air, so he said, it's important to know whether the building is well-ventilated.

"In some cases, air conditioning can be a risk factor but usually isn't," he said. "If a building is properly ventilated, has a good supply of outside air, and it has good air filtration, then the risk of aerosol transmission at a distance from the infected person is probably pretty low."

Han said if there's a big group of people, nothing beats the outdoors.

"So things get diluted much more quickly and there's sort of random air currents. The other thing about being outdoors is that there's sunlight. and we actually think that light in particular UV light can kill the virus," she said.

Both say proper social distancing is still key. Bahnfleth said to make sure there is enough fresh air circulating and upgrade any air filters.

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