Do masks help protect you from wildfire smoke?

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As wildfires scorch Canada and smoke blankets the United States from Minnesota to New England and south to Florida, millions of people are under air-quality alerts.

Face masks — the same kind used in the COVID-19 pandemic — can help protect people from dangerously polluted air, say health experts.

But choose a good quality mask, they caution.

"N95 masks are the type of face covering protection that I would recommend for somebody who is outside during the air pollution caused by wildfires," Marina Vance, PhD, an assistant professor in the environmental engineering program at the University of Colorado, Boulder, told Healthline.

Masks that are rated KN95 are also effective, according to Vance, who has tested the masks in her laboratory. "These are both very efficient masks; I would trust them both," Vance added.

Simple cloth masks, scarves and other cheap alternatives aren't effective at filtering out the small particles in smoke.

Small particulate matter in the smoke is "where a lot of the toxic stuff lives," John Granton, a respirologist at Toronto General Hospital, told Yahoo Canada.

"That's not filtered by your upper airway, that gets access to your lower airway and into your bloodstream even — and that's where the danger lies," Dr. Granton said.

"That can cause asthma attacks, can cause heart attacks, can contribute to hospitalizations and has long-term health outcomes," Dr. Granton added.

It's also important to wear the mask correctly: It should cover your nose and chin and sit tightly on your face, according to the Washington State Department of Health.

In their factsheet "Wildfire Smoke and Face Masks," the agency also warns that surgical masks and paper masks with a single strap "will not protect your lungs from wildfire smoke."

Additionally, a mask should be thrown out after it's used a few times. N95 masks aren't meant to be reused, even if they’re cleaned, because they become less effective after each use.

Young children and people with respiratory illnesses like chronic pulmonary obstructive disease, asthma or other conditions may need to take special health precautions, including evacuating an area that's under an air-quality alert.

New York City's air has been heavily polluted by thick smoke from Canadian wildfires burning hundreds of miles away.

NYC Mayor Eric Adams warned residents to stay inside to avoid exposure.

The haze wafting in from Quebec poses a threat "even to healthy adults."

New York's air quality has become some of the worst in the world as the ominous orange smog from wildfires near Quebec, British Columbia and Nova Scotia continues to settle over the region, according to IQair.

​​The air quality is expected to remain hazardous through the weekend.

If you don't need to go outside, then don't. "Most people recommend staying indoors as much as possible and not exercising or doing things outside," Dr. Granton said.

Indoors, Vance recommends using an air purifier with a HEPA filter. Other suggestions include sealing windows, setting air conditioners to recirculate indoor air and checking that smoke and carbon monoxide alarms are working correctly.