One thing you're doing with your mask in a car could put both you and others in danger: hanging it from the rearview mirror.
Jade Flinn is a nurse educator at Johns Hopkins Medicine*… and she says, if you hang your mask from the *rearview mirror, and have the AC blowing on it - whatever is on your mask is now blowing around the inside of the car. It’s just like being in the car with a person who’s infected. Being in an enclosed space with recirculated air can spread the virus.
The safest thing to do in a car right now is to keep your mask on and roll down the windows, especially if there are passengers in the car who you don't live with. Or use the car’s air conditioning to bring in outside air.
According to the Harvard School of Public Health, when the windows are closed, the fine aerosol particles that cause COVID-19 accumulate in the car cabin. And the concentration can build up if there’s no significant dilution happening. But even cracking one window open just three inches can produce a tenfold reduction in the amount of virus in the cabin air.