The World Health Organization recently said that to reduce viral spread, buildings should have ventilation that changes the total volume of air in a room at least six times an hour. Although there’s wide variation in how different spaces are ventilated, some hospitals, planes and new buildings may change the air as much as 12 times an hour. Some schools and restaurants may have air exchange rates of three to five times an hour.
By comparison, the air in a typical home changes only about every one to two hours, said Shelly Miller, professor of mechanical engineering and a ventilation expert at the University of Colorado, Boulder.
“I’ve been concerned that people are not completely understanding how ventilation in the home is different than ventilation in commercial spaces or schools or hospitals,” said Dr. Miller. “I want people to understand that their homes are generally not ventilated. If you have friends over for dinner and someone is infectious, aerosols can build up.”
Depending on the home, weather conditions and other variables, research shows that opening multiple windows — the wider, the better, and in every room if possible — can increase the air exchange rate to as much as three times an hour. If it’s cold outside, turn up the heat or use space heaters as needed.
Dr. Miller also suggests turning on exhaust fans, which are typically found in bathrooms and over the stove. While those precautions won’t eliminate risk, even a few exhaust fans, combined with opened windows, can help.
“Exhaust fans were put in homes specifically to take out contaminants that are a problem,” said Dr. Miller. “You are creating a negative pressure inside the space, sucking air out at a higher rate.” (Don’t use a regular fan, she warns, which just moves air around the room and can increase risk to the group if someone nearby is infected.)
A portable air cleaner can also reduce risk, but buy an appliance large enough for the room size, or obtain multiple air cleaners for a large space. Use this online search tool from the Association of Home Appliance Manufacturers and read more from Wirecutter, a New York Times company.