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Feb 19, 2025

Doctors Still Recommend Masking After a Wildfire. Here’s Why. | Reviews by Wirecutter

By Katie Okamoto Katie Okamoto is an editor on the discovery team. She’s covered the intersections of products, sustainability, and health for more than a decade. After an urban wildfire, as the smoke

By Katie Okamoto

Katie Okamoto is an editor on the discovery team. She’s covered the intersections of products, sustainability, and health for more than a decade.

After an urban wildfire, as the smoke clears and air quality index readings lower, serious health risks may still linger.

You should definitely wear an N95 mask if you smell smoke or see ash, as our colleagues at The New York Times reported earlier this week, due to the immediate health impacts of breathing urban-wildfire smoke. You should also wear one if you are at or near a burned or smoke-damaged property.

That’s because a single intense exposure to smoke and particulates has the potential to cause long-term cardiovascular and respiratory effects, said Dr. Anna Nolan, a pulmonologist at NYU Langone Health who has researched the impacts of particulate exposures after 9/11.

This type of exposure could increase your risk of reactive airway disease, inflammatory conditions, and even interstitial lung disease and lung cancer, as well as other serious health impacts. Notably, the long-term health effects of some of the things that are released into the air from a major urban wildfire are still being studied.

I consulted eight pulmonologists and two public health experts, and all of them agreed that it’s a good idea for people in the area of an urban wildfire, like the one the Los Angeles region is experiencing, to exercise precaution and continue to wear a high-quality, well-fitting mask outdoors in the days—and perhaps even weeks—following.

Here’s what you should know.

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When you want to get a general sense of outdoor air quality, the air quality index, or AQI, is typically an especially useful tool.

AQI is a composite number that categorizes the concentrations of five major pollutants regulated by the Clean Air Act—particulates of certain sizes (below 10 micrometers, or PM10, and below 2.5 micrometers, or PM2.5), ozone, carbon monoxide, sulfur dioxide, and nitrogen dioxide—into health-risk ranges.

But relying on AQI alone has limitations, especially after widespread structural fires like the ones in parts of the Los Angeles area. This number doesn’t capture all of the pollutants that may be released into the broader environment from burning buildings and their interiors and their exposure to extreme heat. Those potential toxins include volatile organic compounds, polycyclic aromatic hydrocarbons, lead, asbestos, plastics, and other possibly pathogenic materials, experts say.

Additionally, AQI is measured by a network of sensors, which aren’t always well distributed or in your immediate area, said Dr. Stephanie Christenson, an attending physician in the pulmonary clinic at University of California San Francisco. As a result, the AQI reading you see for your city on AirNow or in other applications may give you a false sense of safety.

And a sensor may not capture airborne exposures in your immediate vicinity, such as from particles that get kicked up from vehicles, wind, and people’s activities, said Joseph Allen, associate professor of exposure assessment science at Harvard T.H. Chan School of Public Health, in an email. Without rains to wash them away, potentially dangerous particulates that have settled out of the air can “easily be thrown up back into the air,” said NYU’s Nolan.

“I tell everybody to take the numbers with a grain of salt,” said Dr. Irina Dralyuk, a pediatric pulmonologist at Cedars-Sinai Guerin Children’s in Los Angeles, in a phone interview.

More research is needed to understand what may be in the outside air after an urban wildfire and for how long, said Dr. Kari Nadeau, chair of the Department of Environmental Health at Harvard T.H. Chan School of Public Health, in an email.

Some of researchers’ understanding about potential long-term effects comes from studies done after September 11, 2001, in which many frontline workers, volunteers, and civilians were exposed to dust, ash, and smoke in the days and weeks after the World Trade Center attack. A 2010 study found that this exposure led to substantial—and persistent—declines in lung function among first responders, and a more recent study looked at cancer characteristics of community members, who may have had chronic exposure to dust in the weeks after the disaster.

What is more certain is that if you have underlying respiratory or cardiovascular conditions, such as asthma or COPD, even low exposures to pollutants can pose a risk and exacerbate your existing conditions. If you are experiencing symptoms, like cough, wheezing, chest pain, dizziness, headache, or difficulty breathing, even if they are mild, seek medical attention as soon as possible. It may take four to six weeks after initial exposure to feel respiratory symptoms, said Dr. Panagis Galiatsatos, a pulmonologist and associate professor of medicine at Johns Hopkins School of Medicine.

Even if you have already been exposed to affected air after a fire, it’s not too late to protect yourself. Experts I spoke with said to do your best to limit further exposure by limiting your outdoor activities as much as you can, choosing less strenuous activities when you are outdoors, and wearing a tight-fitting N95 respirator mask (or higher protection, like P100) when outside. Some experts I spoke with said that a quality KN95 would also provide significant protection outdoors, though the highest possible protection is advised at or near a burn site or in areas where ash has fallen.

Note that N95 masks do not protect against vapors or gases from fires, only particulates. They also may not protect against asbestos fibers that may be in the air, said Dr. Jamie Garfield, a professor of thoracic medicine and surgery at the Lewis Katz School of Medicine at Temple University in Philadelphia, in an email through the American Lung Association.

“Asbestos fibers are well <10 microns and would not be filtered out by even some of the best masks,” said Garfield; they may be as small as 0.1 micron. She added that NIOSH-approved N95 and P100 masks filter most particles down to 0.3 micron in size when worn correctly. Heavy metals, like lead, which are larger, “should be adequately filtered by most masks” with N95 ratings and above, Garfield further explained.

Galiatsatos noted that you may want to think of it in terms of exposure over time and proximity to the burn site. He said he would advise anyone to continue to mask out of precaution “if you had a massive exposure initially” and you’re now returning.

Beyond considering your prior exposure and proximity to the burn area, people who are especially vulnerable are infants, children, pregnant people, those over 65, and those with underlying respiratory or cardiovascular conditions. As always, it’s best to discuss your personal risk with a physician.

Given the unknowns and potential long-term risks, Dralyuk suggested that everyone who can should exercise caution and wear a mask even when AQI readings are 40 and above (51 to 100 is considered “moderate” AQI), due to the index’s limitations.

“Even if someone is just a healthy, young person, I would take this very seriously,” said Dralyuk, due to the potential for serious long-term impacts, including from potentially carcinogenic exposures.

When masking, fit is as important as the filtration level you wear, said Christenson. In addition to Wirecutter’s guide to respirators for wildfire smoke and dust, we have a guide to KN95 masks for kids and toddlers. Cloth masks are not advised, but a high-quality KN95 may offer a better fit for smaller faces, said Christenson.

Relatively comfortable, this mask filters out 95% of airborne particulates.

Otherwise similar to the 3M 8511, this model lacks an exhalation valve.

This half-facepiece reusable respirator is comfortable to wear and widely available in multiple sizes. It can be over 99% effective at filtering a range of airborne particles and some fumes.

“It’s important to be vigilant about monitoring your local air quality and be conscious of both outdoor and indoor environments,” said Dr. Sonali Bose, associate professor of medicine (pulmonary, critical care, and sleep medicine) and pediatrics at the Icahn School of Medicine at Mount Sinai, in an email.

Harmful particles can also cling to your clothing and hair and reenter indoor air once you’ve come inside. Soon after returning, you should change out of your outside clothing and wash your hair, said Galiatsatos.

Indoors, continue to run air purifiers or use central air. If you can, upgrade your HVAC filter to a MERV 13–rated filter or higher, advised Allen. If you smell lingering smoke inside, Wirecutter has advice on how to clear your space of wildfire smoke and a guide to the best air quality monitors for your home.

I asked Dralyuk, who lives and practices in Los Angeles, how long she advises taking air-quality precautions after an urban wildfire dies down. A pediatric pulmonologist, she said that she’s telling families with children to wait at least two weeks until a fire is fully contained to return to the area. “But for masking, I would say probably weeks.”

Nadeau, who spoke on a panel at Harvard’s T.H. Chan School of Public Health late last year on the dangers of wildfire smoke over widespread areas, suggested a month of masking.

“Realistically, for probably weeks, if not longer, after the fires are extinguished, we’re going to have lasting impact on health in terms of our air quality, whether we can smell it or not,” Dralyuk said. “The exposure to particles in our air is a risk for everybody.”

This article was edited by Maxine Builder and Megan Beauchamp.

These masks work to block particulate inhalation in conditions ranging from wildfire smoke to dusty home projects.

HEPA air purifiers, such as our picks from Coway and Airmega, are excellent at filtering wildfire smoke from your home’s air.

The best kids mask to safeguard against COVID-19 is the most protective one they’ll keep on. We have four to recommend that fit a range of ages and are high-performing and breathable.

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Katie Okamoto

I focus on the intersections of shopping, sustainability, and environmental health. I also lead and advise on standards for reporting on environmental impacts and green marketing claims of products in Wirecutter’s coverage.

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