Masks for Smoke and COVID-19 — What Kind Is Best?

3M brand N95 particulate respirators are displayed on a table on July 28, 2020 in San Anselmo, California.  (Justin Sullivan/Getty Images)

With hundreds of wildfires burning across the state, and huge complex fires affecting the air quality in nearly every Bay Area county, residents are understandably wondering how to deal with multiple crises: raging fires, widespread smoke and the coronavirus pandemic.

In the "before times" — pre-COVID-19 — residents in smoky areas would avoid going outside and would stock up on N95 or N100 masks to protect themselves from the fine particulate matter that gets into the air when a wildfire burns, which can have some nasty affects on your health.

Thursday, August 20, 2020 off Pleasant Valley Road in Vacaville. (Peter Arcuni/KQED)

But, with those masks in short supply and desperately needed by health care workers and first responders on the front lines, how can Californians best protect themselves from fires and COVID-19?

In short: it's not clear. Even the Centers for Disease Control and Prevention can't give exact advice on what the best path forward is. These simultaneous events are unprecedented, so here's the best advice we can give, for now, and we'll update this post when we know more.

Cartoonist Mark Fiore's Take

I Have an N95 Mask, Should I Wear It?

The best masks for filtering out wildfire smoke are either in short supply or have exhaust valves, which don't effectively prevent the spread of the coronavirus. Simultaneously, a cloth mask — which is mostly effective at stopping the spread of the virus — isn't great at filtering out wildfire smoke.

What should you do?

Here's what we know: An N95 mask without an exhaust valve is still one of the best ways to prevent the spread of COVID-19 and protect yourself from the smoke.

So, if you have one you've been saving and you want to wear it, go for it. But remember, those masks are in short supply and should be reserved for health care workers. So don't rush out to stockpile them.

Plus, some public health officials say they're not for everyone. Veronica Vien, a public information officer for the San Francisco Department of Public Health, said that they can be uncomfortable to wear for long periods of time and must "provide a tight seal around the wearer’s mouth and nose" to work effectively.

"If an N95 respirator makes you feel better, wear it. If you feel worse, please don't!" Vien said.

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So, What Should I Wear?

If your N95 does have an exhaust valve, you do have a few options. Some, like UCSF pulmonologist Dr. John Balmes, have found creative solutions.

"I put a piece of masking tape over the valve when I go into a store. So then I'm protecting myself and others," he said.

His wife has also found a workaround.

"She puts a surgical mask over her N95 exhalation valve," Balmes said.

While some public health officials have recommended wearing two masks to prevent both wildfire smoke inhalation and the spread of the coronavirus, there is no consensus — as of yet — on this issue. You should check with your health care provider, if possible.

The next best thing? A surgical mask.

"They're actually somewhat protective with regard to wildfire smoke because they’re standardized," Balmes said. "It's about a third of as good, on average, as an N95."

Cloth masks are least effective against smoke, Balmes said, but you should wear them anyway. Because wildfire smoke or no, protecting other people from the virus is still important.

What Else Can I Do to Protect Myself?

While masks are a good option, public health officials say the most effective way to keep yourself safe from wildfire smoke is to stay inside.

Below is an interactive, crowdsourced air quality map from the private company PurpleAir. More information on air quality can be found here.


This advice may not feel particularly helpful or possible during a heat wave and with impending evacuation orders, but officials with the state Office of Emergency Services still recommend that residents stay indoors with the doors and windows shut and with the air conditioning running if possible.

The California Air Resources Board also recommends mechanical air cleaners with a high efficiency particulate air (HEPA) filter that collects very small particles and does not emit harmful substances. These air cleaners can dramatically reduce indoor particle levels, in some cases by more than 90%. See a list of devices here.

If you don't have air conditioning — which makes closing doors and windows especially difficult during a heat wave — consider getting some battery-operated fans and reducing activities that increase indoor air pollution, like burning candles, cooking on gas stoves or vacuuming.

Want to get this information in cartoon format? Check out KQED's Mark Fiore's take here — and share it, too!