N95 Masks Helped Protect Against the Coronavirus. They Also Work Against Wildfire Smoke.

Today’s the day to put that mask back on.

As smoke from wildfires in Canada drifts over large parts of the United States, the best thing to do to prevent breathing in pollutants on Wednesday is to stay indoors. For many people, of course, that’s impossible. So if you do have to brave the outdoors, putting on a mask is the next best thing.

But beware, not all masks work equally well. A surgical mask, scarf or bandanna won’t do much to keep you from breathing in pollutants.

N95 masks can filter tiny particles that are less than 0.3 micrometers. By comparison, the width of a single human hair is approximately 60 micrometers, according to California’s health department.

Instead, use N95 face masks (you may still have some of those left from the pandemic), or respirator masks, which you can find in hardware stores or online. Make sure to cover both your nose and mouth.

“Air quality is at unhealthy levels in New York today due to wildfire smoke drifting down from Canada,” Lucky Tran, a scientist, wrote on Twitter. “Reminder that N95 masks help protect against smoke too. It’s a good idea to wear a mask outside today!” He also advised people to turn on indoor purifiers.

People in areas affected should take the smoke seriously, experts warned. “Wear N95 or better masks and stay inside if you can, with air purifiers,” Mask Oakland, a project that responds to smoke in the Bay Area-based community organization, advised.