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Prof. Don Milton Discusses Study Suggesting Air Conditioning Systems Can Spread The Coronavirus

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Donald Milton, faculty member of School of Public Health at the University of Maryland

The findings of a new study suggest that air conditioners can blow around infected droplets hanging in the air, Don Milton told WBUR. With enough air movement, your nose can pull in large particles, he said. 

“Outbreaks — where you have a bunch of people infected all at once like that — are almost exclusively occurring indoors in poorly ventilated environments," Milton explained. 

Even some popular systems don't bring in fresh air or provide filtration. They are energy efficient, but they just recirculate the air, he said. Ceiling fans also move the air around but don't limit the spread of the coronavirus. 

Through air dilution or ventilation coming from outdoors, researchers find each person in a room should have 5 to 10 liters of fresh or filtered air per second, Milton said. Fresh air dilutes the virus and reduces the level of exposure. New data also shows sunlight works as a disinfectant, but that doesn't mean that people should break social distancing rules outside. 

Milton told WBUR that UV light in the air ducts of air conditioning systems has been used to control bacterial and fungal growth on the cooling coils, and UV lights also have the potential to be highly effective against COVID-19.

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