MINNEAPOLIS (WCCO) -- As the weather heats up, homes and offices will start running air conditioners, circulating what people breathe. So, that had some WCCO viewers wanting to know: Can AC put us at risk for COVID-19? Good Question.
"What we've been able to learn so far is there's no evidence that contaminated air taken from one space and put through an air conditioning system into another space has been found to cause infections," said Bill Bahnfleth, a professor of architectural engineering at Penn State University.
Bahnfleth is also the chair of an ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers) task force that provides guidance to ensure buildings are prepared for epidemics.
"We have to understand that air conditioning means not just heating and cooling," he said. "It also includes things like bringing in outside air for ventilation and filtration to remove particles."
Researchers at the University of Oregon created an animation that shows what happens to the virus particles in a room once outside air is introduced and exhausted.
"What we were seeing is that, with increased outdoor air exchange, through the open window… particles deposit more quickly and then also be exhausted from the airstream more quickly," professor Kevin Van Den Wymelenberg of the University of Oregon told CBS This Morning.
In most HVAC systems, filters stop the big droplets and ventilation dilutes virus particles in the air.
"Properly operated ventilation is our friend," said Pete Raynor, a professor of environmental health sciences at the University of Minnesota. "It can reduce infection levels."
Each expert stressed the answer as to whether air conditioning can spread COVID-19 isn't so simple. That's because scientists don't know exactly how much of the virus is transmitted through close contact versus particles that have been aerosolized. It's also because air conditioning systems differ all across the country and the world.
One study from a restaurant in China found one person spread the virus to nine people in poorly ventilated space.
"Ventilation systems are complicated and vary from place to place," Raynor said.
Bahnfleth said this is a good reminder that people that they should be aware of their HVAC systems and how they work. The ASHRAE task force recommends bringing in an engineer to look at a building's system and ask: Should the filters or ventilation be upgraded?
"The thing we have to re-emphasize is that as far as we know the transmission is from people being close together," Bahnfleth said. "This is on top of all the things we've been told to do – social distancing, hygiene and masks."
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