When engineer Devabhaktuni Srikrishna learned of the Covid-19 preparedness plan at his children’s school in San Francisco he knew it was short-sighted—the school planned to circulate air from outdoors through the classrooms to improve ventilation and hopefully reduce viral transmission.
“This is a fine strategy when you can get air from outdoors, but they had no solution for the fall when there could be wildfires and you don't want to breathe the air from outdoors,” says Srikrishna, founder of Patient Know How, a site where he rates masks with high-quality fit and filtration.
Instead, he and a team of parents fundraised to supply teachers with portable air filters that could cleanse the air of both contagious viral aerosols and toxic wildfire smoke pollutants.
Last year, communities across the West faced the dual crises of a deadly wildfire season and the Covid-19 pandemic. This summer, Covid-19 cases are once again on the rise, partially due to the spread of highly contagious viral variants. The wildfires, too, have become intense following years of drought and an unseasonable heat wave. The Bootleg Fire has torn its way through Oregon, burning a swath of land larger than the city of Los Angeles. Some smoke plumes have gotten so large, they’ve begun creating their own weather patterns.
And with smoke spreading thousands of miles to the East Coast, the issue of wildfire-induced air pollution may no longer be a regional issue.
“This is becoming a chronic exposure,” says Tarik Benmarhnia, a environmental health scientist at the University of California, San Diego. “[Wildfires] used to be, I would say, a very extreme event that may take place every few years. We can't say that anymore.”
Fortunately, you can take steps to protect yourself and loved ones from wildfire smoke exposure. Here’s what you need to do to keep yourself safe.
Assess the dangers of wildfire smoke exposure
Wildfire smoke is comprised of various gases and particles with different chemical make-ups. Though many of these components can be toxic, the most harmful are tiny particulate matter called PM2.5. These particles measure 2.5 micrometers in diameter, or about 1/30th the width of a human hair.
Due to their small size, these particles can be inhaled deep into the lungs and sometimes make their way into the bloodstream. There, they can wreak havoc on the body’s vital organs, causing cardiovascular, respiratory and even neurological problems. Studies have linked PM2.5 exposure to asthma, stroke, eczema, some cancers and more.
Such particles arise in air pollution from traffic, industry and agriculture. But the ones found in wildfire smoke appear to be much more harmful to the body. In a study published in March in Nature Communications, Benmarhnia’s team found that PM2.5 from wildfire smoke can drive an increase of ten percent in hospital admissions for respiratory issues, compared to PM2.5 from other sources.
When high levels of PM2.5 accumulate in the air, a greyish haze is sometimes visible. Other times, the particulate matter remains largely invisible. That’s why checking the air quality in your area is important.
The Air Quality Index is a metric developed by the Environmental Protection Agency which runs from 0 to 500, with 500 being the most polluted. It accounts for five major air pollutants: ground-level ozone, particle pollution (including PM2.5), carbon monoxide, sulfur dioxide and nitrogen dioxide. The scale is color-coded to help members of sensitive groups and the general public quickly understand how polluted the air is. Sensitive groups include children, older adults, individuals with respiratory or heart conditions, individuals who are pregnant and outdoor laborers with prolonged exposure to smoke.
When the Air Quality Index is in the green, yellow or orange zones, at 150 or less, it’s generally safe to be outdoors. At 150 or more—in the red, purple and maroon zones—most individuals are susceptible to negative health effects and those especially sensitive to air pollution should be extra cautious. At these levels, the EPA recommends staying inside when you can, wearing a mask when you can’t and limiting strenuous outdoor activities like exercise.
To learn the real-time Air Quality Index near you, you can visit AirNow.gov, a collaborative site by the EPA, National Oceanic and Atmospheric Administration, National Parks Service, NASA and more. The site uses research grade instruments to report an accurate Air Quality Index, though the instruments can be spaced far apart.
Another site, called Purple Air, crowd-sources data from air quality monitors in homes across the U.S. Users report the Air Quality Index from inside or outside their homes and the numbers are presented in a multi-colored map that demonstrates air quality with a more detailed picture of where polluted air settles.
When air quality is particularly poor, Marina Vance, an engineer at University of Colorado Boulder, says it’s best to avoid going outside all together. When being outdoors is necessary, it’s key to find a high-filtration face mask.
As is true when protecting yourself and others from Covid-19, Vance says that any face covering will be better than no face covering. But unlike Covid-19, harmful particles from wildfire smoke can easily penetrate cloth coverings and weasel through gaps between the mask and a person’s face.
“In the context of wildfires, one potentially dangerous thing is that people will feel like they're protected when they're not,” Vance says. “They're going to go out when there are wildfires and air pollution and they're going to put on this cloth mask that has lower filtration efficiency and have this sort of misguided sense of security.”
The most important factor, Srikrishna says, is how well the mask fits your face. No face covering will effectively keep out pollutants or viral particles if leaks are present. If you wear glasses and they fog up when you’re wearing a mask, it’s a good indicator that the seal is not tight enough.
Masks are rated based on how much particulate matter they can filter out when fitted properly. For instance, an N95 mask will keep out 95 percent of particles, while a P99 will filter 99 percent.
“This is what these n95 masks are designed to do—help maintain breathability while providing good filtration. And that works regardless of whether you're talking about Covid or you're talking about wildfires,” Srikrishna says.
Srikrishna’s favorite mask features a semi-flexible N95 filter and a robust rubber silicone gel seal around the edges. Other versions have a solid plastic frame and round, changeable filters on each side of the mouth. For individuals accustomed to wearing disposable surgical masks, some companies create straps to fit over top which create a seal strong enough to classify the product as an N95.
N95 and other high filtration masks are especially effective because they hold an electrostatic charge. Just as socks can stick together when pulled from the dryer, small particles will stick to the electrostatic properties of the mask.
Though demand from the Covid-19 pandemic and wildfire season may dry up the supply of disposable N95 masks, Srikrishna says other, highly rated respirators are available.
“Just like buying shoes, there are so many different types and so many manufacturers,” Srikrishna says. “You’ve got to find one that fits you well and provides aerosol filtration.”
Buy the right air filter
Staying inside on hazy days can protect you significantly from wildfire smoke exposure. Still, polluted air can leak into a building, increasing health risks particularly for individuals who are immunocompromised or with preexisting conditions. Vance recommends sealing off possible passageways by closing all doors and windows and using air conditioning for ventilation if you have it. In some extreme conditions, consider adhering plastic sheeting around the windows to ensure a better seal.
To purify the air in your home or building, you can purchase a variety of different portable air purifiers. Many of these work by using a fan to circulate air through a High Efficiency Particulate Air (HEPA) filter. HEPA filters, which have been in use since World War II, continue to be the standard filtration technology. Made of many randomly arranged fibers, these filters mechanically absorb tiny airborne particles like pollen, dirt, dust and some bacteria and viruses.
“Keep it simple and don't get fancy,” Vance says. “There are some portable air cleaners that use ionization technologies, electrostatic precipitation and all sorts of bells and whistles. Honestly all that you really need is a filter.”
Srikrishna emphasizes that when buying an air filter, individuals should account for the size of the room they’re trying to purify. Because square footage calculations are non-linear, he says individuals commonly make the mistake of underestimating how much filtration power they’ll need. If, for example, you purchase a filter rated for a 15-by-15-foot room (225 square feet), you’ll need four to properly purify a 30-by-30-foot room (900 square feet).
These filters can be used to clean the air from both air pollution and SARS-CoV-2, the virus that causes Covid-19. “When you use it for Covid prevention inside of a shared setting, you need to turn it on maximum,” Srikrishna says, noting that most filters are designed to detect particles and won’t capture virus-carrying aerosols if left on an automatic setting. “It’s a very simple thing, but it makes all the difference. Otherwise, it's not doing anything.”
If you have a heating, ventilation, air conditioning (HVAC) unit in your home, you can also install filters to cleanse air as it circulates the building. Opt for a HEPA filter that has a MERV rating of 13 or higher. Even on temperate days when your air conditioning is off, Vance recommends running the central fan with the filter in place for an extra cleanse.
For those who find purchasing portable air filters or running the air conditioning is too costly, researchers are testing the efficacy of a DIY solution that involves attaching a MERV 13 or HEPA filter to a standard box fan to create some filtered ventilation.
Reduce other forms of pollution
On an individual level, there’s not much that can be done to prevent or halt active wildfires. As the West grapples with the smoke, Benmarhnia says considering the inequitable impacts of air pollution on communities is important.
“Everyone is exposed to [wildfire smoke], but we don't start from the same place,” he says. “Some individuals are already vulnerable because they live in polluted areas from other sources, in a very hot environment or with a specific occupation that may expose them to other issues and stress that may not play well in relation to wildfire smoke.”
To limit these extra sources of pollution, consider driving less, nixing wood stoves and limiting use of gas-powered equipment when air quality is poor. For individuals whose occupations require them to be outdoors for most of the day, like agricultural laborers and construction workers, wearing protective clothing and a well-fitting mask can limit skin and lung exposure.
Regardless of how you choose to protect yourself from air pollution, it’s best to make a plan now, before wildfires get much more intense.
“Planning ahead is a smart idea,” Vance says. “These products tend to disappear from the shelves when a wildfire hits to your area.”
Editors' Note, August 11, 2021: Due to a mathematical error, this article originally misstated the number of air filters to purify a 30-by-30-foot room. The correct number is four.