Don’t toss your masks: How to use N95s and other air filters for fire season

In Berkeley and beyond, it’s not too soon to prepare for unhealthy air days.

Poor air quality in Berkeley in August 2020. Credit: Pete Rosos

Public health officials have made it clear: People fully vaccinated against COVID-19 can go unmasked outdoors and in many indoor settings starting June 15. Here in Northern California, though, respirator masks will continue to be part of our daily lives to shield our lungs from smoke during wildfire season.

Experts expect California’s wildfires to be even worse this year than last year’s record-breaking season, continuing a trend of increasingly unhealthy air quality days. They are warning residents to start preparing now. 

Cal Fire says fire season in California is starting earlier and ending later each year, with climate change being a key driver. The length of the fire season, which historically began in the fall, has increased by 75 days across the Sierras. In 2017, the Bay Area saw 28 Spare the Air days. In 2020, the region experienced 46. 

Not knowing when fire season will start, experts are telling people to get ready now, as key safety products can be hard to come by when the smoke arrives.


“It’s weird to be talking about this in June,” said Quinn Redwoods, founder of Mask Oakland, which helps get N95 respirator masks to unhoused and other vulnerable people. “I guess it’s time.”

Experts also suggest that people start looking at ways to improve their homes and their own bodies to adapt to living in an area with regular days where the air is toxic.

“Now is the time to get into great aerobic shape. Now is the time to get your old, leaky window fixed,” said Thomas Dailey, a pulmonary and critical care specialist with Kaiser Permanente Santa Clara who served three terms as chair of the Bay Area Air Quality Management District Hearing Board, a state agency that helps enforce air quality rules. “This is our window of opportunity to prepare.”

For wildfire smoke, opt for N95s or KN95s, not cloth masks

Preparing for fire season starts with acquiring masks adequate enough to filter out the particulate matter in wildfire smoke that can remain suspended in the air for several weeks. Masks are one of the least expensive forms of protection against smoke and fallen ash, especially outdoors. But it’s important to note that many of the masks worn during the pandemic—disposable paper masks, cloth masks, etc.—are ineffective at blocking out the fine particulate matter contained in wildfire smoke. 

“Unlike with COVID-19, a cloth or surgical mask won’t protect a person from poor air quality and smoke,” said Neetu Balram, spokesperson for the Alameda County Public Health Department.

To filter out smoke, the Environmental Protection Agency recommends people use an N95 respirator mask—the highly sought-after face coverings most needed by frontline healthcare workers during the pandemic. Both the N95s with and without valves provide adequate protection against smoke, but the valved masks don’t prevent a person from potentially spreading COVID-19 when they exhale.

The key in using these masks is ensuring a tight seal around the nose and mouth, which can be difficult for people with facial hair. Double masking, or using a cloth mask over an N95, can help create a tighter seal. The same is true with a KN95 mask, or N95 equivalents made in other countries that haven’t been screened by the U.S. National Institute for Occupational Safety and Health.

Balram says N95 masks may make it difficult for some people to breathe and may be dangerous for people with certain lung and heart conditions. There also aren’t any N95s certified for children, she said. 

The CDC encourages parents to keep kids indoors, especially if they have asthma, allergies, or chronic health issues, and prepare for evacuation if children have trouble breathing or other symptoms that do not get better.  

When and how to get N95 masks

Mask Oakland organizers, Quinn Redwoods and Dennis Uyat moving donated masks from a storage facility last year. Credit: Amir Aziz

In the past, it’s been difficult to get N95s both online and in-person, especially once the smoke has arrived. That’s why Redwoods started MaskOakland in October 2017 in response to the Tubbs Fire to make sure vulnerable people had access to masks during critical moments. That effort continued in 2018 during the Camp Fire, in 2019 with the Kincaid Fire, and through the worst fire season in recent history in 2020. 

Redwoods said that they’ve seen the very concept of wearing a mask go through a political and logistical story arc in just four years. But in that time, they’ve made the right connections and have been able to secure masks more efficiently and in larger quantities. Mask Oakland distributed 100,000 KN95 masks during last year’s fire season through the end of the year. 

Redwoods described the availability of N95s on a recent June evening as “refreshingly normalish.” But Redwoods says it’s important to buy now to avoid a rush. They compared the potential demand for N95 masks when the smoke returns later this year to the early days of the pandemic when people were hoarding toilet paper. 

“Every family, every household should have a couple of N95s for each person on hand,” they said. “Do you want to experience the toilet paper issue with your ability to breathe?” 

N95 and KN95s are available online and in local hardware stores. Brian Altwarg, general manager of Markus Supply Ace Hardware in Jack London District, says N95 masks without valves “are pretty much gone,” as healthcare workers have needed them during the pandemic. But his store has N95s with valves in stock with a three-per-customer limit. KN95 masks are also available at the store and his supplier’s warehouse in Rocklin. 

Right now, Altwarg said, masks aren’t flying off the shelves. “That all changes when the air gets bad,” he said. 

Purifying air indoors

Besides having the right masks, there are other ways experts suggest you prepare for wildfire season. 

The California Air Resources Board recommends people consider permanently installing a ventilation system that filters outdoor air before it enters their home to protect against long-term or recurring episodes of air pollution, like seasonal wildfire smoke. 

For many, that may not be feasible. 

Purifying indoor air requires a filter—whether for a home’s HVAC system or a portable air purifier—with a Minimum Efficiency Reporting Value (MERV) of 13 and above. Thirteen is the lowest-rated filter used in smoking lounges, but anything rated 16 or higher does a good job filtering wildfire smoke, according to the CARB ratings

Redwoods recommends investing in a portable air purifier and an extra filter (the original may need to be replaced before another becomes available at the peak of the season.) The cheapest model on Consumer Reports’ best air purifiers for wildfire smoke is $220, although they’ve put their stamp of approval on models as cheap as $60. Other models are available at local hardware stores and big box retailers, although all are susceptible to supply chain issues during an emergency. 

One low-cost upgrade that can be shared with neighbors who don’t have abilities to plan so far ahead is affixing a MERV 13-16 filter (less than $50 for a six-pack) to a box fan, which Redwoods said is “an N95 equivalent for your house.”

“Air purifiers, unfortunately, are part of our future,” they said. 

The health risks of wildfire smoke 

Wildfire smoke causes a slew of health risks, especially for older people, children, and those with respiratory disorders. Dailey, the Kaiser doctor, said that the aerosolized particulate matter in wildfire smoke is so small that the lungs can’t filter it out, so it is absorbed directly into the bloodstream. 

“That’s why it’s so dangerous,” Dailey said, adding the Bay Area sees an increase in heart attack and strokes during Spare the Air days.

A team of researchers from University of California San Diego looked at data from wildfires in Southern California from 1999 to 2012, specifically the impacts on human health from smoke, ash and dust. Their findings, published in March in the journal Nature Communications, concluded that the particulate matter generated during a wildfire “is up to 10 times more harmful on human health” than particulate matter from other sources. 

Some people are more likely to be impacted by wildfire smoke. According to the U.S. Environmental Protection Agency, that includes children and teenagers because they breathe more per pound of body weight. It also includes older adults, those who are pregnant, and people with diabetes, because they’re more likely to have underlying cardiovascular or lung diseases. 

During wildfire season, it’s important to monitor the AQI, or air quality index, as levels can change by the hour. The best options for monitoring your local AQI is AirNow.gov (run by the U.S. Environmental Protection Agency using government sensors); PurpleAir (run by a technology company using its own private sensors); and IQ Air, whose app is called AirVisual (a Swiss air quality company with its own sensors).

Each of those options display AQI readings as a number and a color on maps. As of this writing, the majority of the Bay Area is green, meaning the concentration of pollutants is scored below 50. That means the air is safe outside. 

People start getting concerned when the AQI reaches above 100, entering the orange stage. That triggers a Spare the Air alert, encouraging people to drive less and use combustible sources of fuel as little as possible. The Bay Area Air Quality Management District, which issues those alerts, says particulate matter is the most common form of pollutant between November and February. And it issued more alerts last year than ever before.

The public health message during bad air days is the same one heard during the pandemic: stay home. Dailey said it’s best to remain indoors as much as possible, as an N95 or KN95 mask only blocks 95% of the particles that can become lodged deep in your lungs and enter the bloodstream. “That means 5% is still getting through,” he said. 

But staying home is not always a viable option for people whose work or daily life requires them to be outside, and those whose homes can’t protect them from the smoke. 

Daily also encourages people to get into good aerobic shape and build up their lungs now and not to exercise outdoors during Spare the Air days. 

One concern last year was when large numbers of people needed to congregate indoors to find relief from the wildfire smoke. While experts expect this to be less of an issue this year given vaccination rates, Balram said that the Public Health Department is coordinating with county agencies on preparation plans.

Redwoods says the increasing heat and fire in California is a “real-time generational climate adaptation,” and we can expect to see more red days every year. “It’s terrifying to deal with the uncertainty,” they said.

For now, Redwoods’ best advice is to prepare for what all the experts say is coming: more wildfires and more smoke. While they’ve witnessed some of the extraordinary things that humans can survive, Redwoods has learned an important lesson: “Preparedness is better.”