A thick cloud of smoke from the fatal California wildfires hangs over San Francisco, obscuring well-known landmarks including the Golden Gate Bridge.
But doctors say that in some cases, the masks may actually do more harm than good.
Dr. Armand Dorian spoke to Inside Edition about the importance of the mask fitting just right over your face.
“In order to be most effective, it has to fit properly over your nose and mouth,” he said. “If it doesn’t, then the smoke is going to leak through.”
Unfortunately, most masks are too big for kids.
"The safest thing for a kid would be keeping them away from any smoke, any inhalation, keep them inside, use air purifiers,” Dorian said.
And if you have health issues like asthma, the mask could actually hamper your breathing.
"If you keep breathing in your own carbon dioxide, that could make you weak and put more demand and stress on the body and the lungs and the heart," Dorian added.
The best advice, he said, is to stay inside with the windows and doors closed until the smoke clears.
Luckily, rain is on its way, the forecast shows.