The vast majority of SARS-CoV-2 transmission occurs indoors, mostly from the inhalation of airborne particles that contain the coronavirus. But in spite of the obvious risks posed by being inside, according to the Centers for Disease Control and Prevention, small household gatherings are driving much of the recent surge in cases.

The best way to prevent the virus from spreading in a home would be simply to keep infected people away. But this is hard to do when an estimated 40% of cases are asymptomatic and asymptomatic people can still spread the coronavirus to others. Next safest is to entertain outside, but if you can't, there are a few things you can do to reduce the risk of spreading the coronavirus.

First—and most important—always wear masks, make sure everyone stays at least six feet away from other people, and don't spend too much time indoors. But in addition to these precautions, making sure the air inside is as clean as possible can also help. I am an indoor air quality researcher who studies how to reduce the transmission of airborne infectious diseases. Using increased ventilation or running an appropriately sized air cleaner or filter can add an extra layer of protection.