How to mask up to protect yourself from wildfire smoke

We’re all familiar with protective masks. Since 2020, many more Americans have adopted them as defenses against airborne droplets that spread COVID and other pathogens. And while the US recently lifted the pandemic public health emergency, there’s another crisis that’s becoming harder to ignore—smoke-belching wildfires exacerbated by climate change.

When wildfire smoke is thick in the air, precautions such as masking can help keep you safe from the toxic gases that fires generate, says Jun Wu, a professor of environmental and occupational health at the University of California, Irvine. Specifically, consider wearing N95 masks or similar respirators. Preparing now for poor air quality is vital, since it is a problem that is likely to worsen as the planet gets warmer. 

Humans directly cause about 85 percent of forest fires, but anthropogenic climate change creates the conditions for more intense flames. According to the National Oceanic and Atmospheric Administration, the increase in temperature and dry conditions have led to larger, more severe, and longer-lasting wildfires. One concern with a more active fire season is the surge in air pollutants emitted from wildfire smoke. And if you’re someone who might think wildfires won’t be a problem in your area, know that smoke can be far-reaching. Just look at how plumes from Canadian blazes choked the eastern United States.

What makes wildfire smoke so toxic?

Wildfires generate a mixture of dangerous gases in the combustion process. These include carbon monoxide, polycyclic aromatic hydrocarbons, and ozone. Long-term exposure to these chemicals can cause a number of health problems. Carbon monoxide makes it hard for the body to deliver oxygen to the brain; ozone can permanently damage your airways; and inhaling polycyclic aromatic hydrocarbons may increase your risk of cancer.

A major concern is the amount of fine particles called PM_2.5 released into the air. (PM_2.5 refers to the 2.5-micron diameter of the particles—smaller than a red blood cell.) These particles are so small they can float, invisible, in the air for up to several weeks. Wind can carry them from a fire’s location to areas hundreds of miles away. They are also easily inhaled and can inflame the lungs and other organs of the body. This is not just a problem of the lungs, but of the entire body, Wu says. When the toxic particles get into your bloodstream and are carried to other organs, they can potentially damage the heart and brain. 

[Related: Wildfire smoke travels far but never really disappears]

“It’s worse than smoking a pack of cigarettes,” explains Norman Edelman, a pulmonologist at Stony Brook University School of Medicine. The irritation from PM_2.5 causes pain in the chest and burning in the nose and throat. It can trigger asthma attacks in people who may not have had asthma before, and make it hard to breathe for people with lung conditions.

What mask should you wear for wildfire smoke?

Similar to pandemic precautions, respirator masks such as N95s are what’s recommended for adults. These masks filter out particles larger than 0.3 microns. N95s provided the best protection against wildfire smoke compared to hospital and cotton masks, a 2021 study in GeoHealth showed. The authors of the research estimated that if everyone wore N95s during a wildfire, it would reduce up to 30 percent of hospital visits. In contrast, surgical masks would decrease only 17 percent of visits, and cotton masks would fare the worst at 6 percent. 

Another option is a P100 or a KN95 mask, which also filter out small particles from air pollution. The only caveat is that both tight-fitting masks can make it harder to breathe if you have preexisting lung problems. Some N95s have exhalation valves, which makes it easier to breathe but may not offer the same level of protection as valveless masks. If yours has a valve, consider layering it with a cloth mask or other covering to create a better seal.

Any mask is better than no mask at all, Edelman says. “But the cloth masks are the least effective,” he adds, “and at least the hospital masks do partially filter out some of the larger particles that enter the nose and throat.” Respirators and surgical masks completely protect against wildfire ash particles larger than 1 micron, a 2022 study found, while cloth masks only partially blocked larger particles from entering the lungs.

[Related: What to do when wildfire smoke fills the air]

Regardless of the type of mask, its effectiveness goes down if not worn correctly. You’ll want your mask tightly secured to your face, covering your nose and mouth. Press down on both sides of your nose to seal the mask, and make sure the two straps or ear loops go above and below the ears. 

There is no set rule for when you have to throw out your mask, though they are not meant to be used forever. It depends on how often you are going outside. You’ll want to check and throw out any masks that are damaged, loose, wet, or if the insides get dirty.

Should children wear N95 masks?

N95 masks are made for adults, not children. Because manufacturers do not make these respirators in children sizes, the coverings would not provide tight face seals and wouldn’t effectively filter out pollutants. Even if you decide to use a cloth or surgical mask, another issue is making sure children wear them properly and don’t pull them down under their noses or chins. Instead, Wu recommends that kids limit their time outside when the air quality is poor. It’s also helpful to have an air purifier in the home.

How long should you be outside to need a mask?

It’s hard to say. Studies haven’t fully investigated whether time limits influence your exposure to danger, both experts say. Instead, Edelman recommends assessing your risk. “It’s dose-related, so the more particles you breathe in, the more likely you are to get symptoms,” he says. Peeking outside for a few seconds won’t do as much harm as working outside from 9 to 5. The bottom line: When in doubt, wear a mask to be safe from wildfire smoke.