Smoke and atmospheric particulate created from the Camp Fire in Butte County created unhealthy air and unusually colored skies on Nov. 10, 2018. File photo: Eric Brandt

Air quality

What do wildfires have to do with air pollution? How do distant fires cause pollution in the Bay Area?

Topography and weather patterns play a large role in why wildfire smoke from hundreds of miles away lingers in the Bay Area, affecting health. 

Also affecting how smoke travels in and around the Bay Area are the Diablo winds — the strong, hot winds that usually blow for at least a few days, usually in the fall, signaling heightened fire risk. 

A high pressure system will develop inland as a jetstream sends hot and dry air down the side of the Sierras and across the Central Valley. The winds typically pick up speed as they whip through coastal mountains. 

The hot and powerful winds have toppled power lines and started fires and created wildfire smoke in the process. That wildfire smoke needs a place to go and for inland areas, that’s typically through the Bay Area and out to sea. 

The smoke can linger in the Bay Area if winds from the Pacific meet Diablo winds.

How bad is wildfire smoke for my health?

Wildfire smoke is especially damaging to the human body because it contains tiny bits of aerosolized particulate matter that the lungs can’t filter it out, so it goes directly into a person’s bloodstream. 

This can trigger a slew of health risks, especially for older people, children, and those with respiratory disorders. Polluted air is associated with heart attack and strokes, primarily in people with pre- existing vulnerabilities such as lung or heart disease. Ongoing research links smoke pollution to other health problems including dementia.

Some people are more likely to be impacted by wildfire smoke, including children and teens who breathe more per pound of body weight. It also includes older adults, those who are pregnant, people with asthma and other upper respiratory conditions, and those with diabetes, because they’re more likely to have underlying cardiovascular or lung diseases.

Research also shows people in lower-income communities are at greater risk for smoke-related health problems. 

I’ve had COVID-19. What do I need to know about wildfire smoke?

If you’ve had or have COVID-19, you may be at greater risk from wildfire smoke, according to the Centers for Disease Control (CDC), because the virus affects the heart and lungs. 

The CDC recommends that anyone with the virus, or who is still experiencing symptoms, make an extra effort to avoid smoke exposure. 

The best protection against the risks of mixing wildfire smoke and COVID-19 is to get vaccinated against the virus. (This is the best way to protect yourself from the virus, smoke or not.)

Some of the symptoms of wildfire smoke inhalation and of COVID-19 are similar, including dry cough, sore throat and difficulty breathing. But other common symptoms of the virus aren’t associated with smoke exposure, such as fever, body aches and diarrhea.

Talk with your health provider about your concerns regarding smoky conditions and COVID-19. 

How can I protect myself from wildfire smoke? When do I need to wear a mask or stay indoors?

With growing bad news about wildfire smoke and health, what can help? 

The public health message during bad air days is similar to the one heard during the worst of the pandemic: stay home. At least on the worst of smoky days. 

When you do go out, make sure you’re wearing a good quality mask (N95 or KN95). These masks definitely help, but still allow around 5% of particulate matter, the bad stuff, to pass through. Make sure the mask has a tight seal around your nose and mouth.

Experts also recommend sealing up your living space as best as possible to keep smoke from getting in, as well as using air filters to cleanse your indoor air. If you can’t smoke-proof your whole house, create a “clean room” to hangout in, or a room protected as much as possible from outside air.

The Alameda County Health Department will also open clean air facilities to the public where you can go to breathe clean air indoors as well as cool off from any heat. When those shelters are open, they’ll be listed on the county’s open Clean Air Facilities page.

Which masks best protect against wildfire smoke?

Masks are among the least expensive forms of protection against smoke and fallen ash, especially outdoors. But many kinds of masks, such as disposable paper masks, cloth masks, etc. are ineffective at blocking out the fine particulate matter contained in wildfire smoke. 

To filter out smoke, the Environmental Protection Agency recommends you use an N95 respirator mask — the highly sought-after face coverings that were most needed by frontline health care workers during the COVID-19 pandemic. They are widely available at  hardware and drug stores, and online. 

Recommendations for N95 masks can be contradictory even among experts. The Centers for Disease Control, for example, states they’re the best choice for fire smoke, but during health care emergencies, these masks should be saved for health care providers. 

While the gold standard for protection, N95s can be tricky to fit, and may be uncomfortable. Still, they’re the best option for smoke-filled air. 

The masks have straps meant to go around the back of your head to create a tighter seal around the nose and mouth, which can be difficult if you have 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 can function well but don’t meet U.S standards. 

Both the N95s with and without valves provide adequate protection against smoke. The valves help keep the mask from overheating, but they don’t prevent a person from potentially spreading a virus, including COVID-19, when they exhale.

N95 masks may make it difficult for you to breathe, which is dangerous if you have certain lung and heart conditions. Ask your medical providers for advice tailored for your health situation.  There aren’t any N95s certified for children because all are too big to fit snugly over smaller faces. For details on protecting children from fire smoke, check out this fact sheet from the US Environmental Protection Agency and the American Academy of Pediatrics.

How can I reduce the impact of wildfire smoke inside of my home?

The key to living indoors during fire season is to keep smoke out, especially if you have or live with someone who has underlying conditions such as asthma or heart issues. 

The California Air Resources Board recommends you consider permanently installing a ventilation system that filters outdoor air before it enters your home to protect against long-term or recurring episodes of air pollution, like seasonal wildfire smoke. For many — such as renters — that’s not 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 or 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 CARB ratings

Experts recommend investing in a good portable air purifier in the earliest days of fires with drifting smoke. 

There are many decent air purifiers out there, ranging from around $100 (for a small space unit) into the thousands. Keep an eye on trusted reviews.

One low-cost upgrade that can be used in a pinch is affixing a MERV 13 filter to a standard box fan.

Other ways to help keep wildfire smoke out of your home include sealing up any drafty areas, such as around older windows or underneath doors. Foam tapes can help create a better seal at the bottom of a door or window. For larger, more problematic areas, consider using a window insulator kit that is installed with tape and a hairdryer.

How can I monitor air quality in my neighborhood?

During wildfire season, it’s important to monitor the AQI, or air quality index, frequently, as levels can change by the hour. You should start getting concerned when the AQI reaches above 100.

There are a growing number of options for monitoring air quality. One trend is toward neighborhood-level monitoring, made possible by crowdsourced data from private sensors. There can be discrepancies and glitches in all systems, but quality control is a big part of the effort. 

The AirNow fire and smoke map draws from both government sensors and private data from PurpleAir.

Here are a few of the most popular options for checking air quality near you: 

Each of the above options display AQI readings as a number and a color, most of which appear on maps updated dozens of times a day. The East Bay remains green for most of the year, meaning the concentration of pollutants is scored below 50. That means the air is safe outside.

When the AQI rises above 100, entering the orange stage, it triggers a Spare the Air alert, encouraging you to drive less and use combustible sources of fuel as little as possible. The BAAQMD, which issues those alerts, says particulate matter is the most common form of pollutant between November and February. It issued more alerts in 2020 than ever before.



The Berkeley Wildfire Guide is a collaboration between Berkeleyside and The Oaklandside. The guide — first published on July 29, 2021, and last updated in August 2023 — was written by Kate Darby Rauch and Brian Krans, edited by Zac Farber and Jacob Simas, designed by Doug Ng and illustrated by T.L. Simons. You can read a version of the guide tailored for Oakland residents on The Oaklandside.

Information overload can be an issue as you plan for emergencies. That’s why we’ve compared information and vetted sources for you, with the aim of providing only credible and recent information from trusted sources. 

Sources used in compiling this guide: CalFire, Berkeley Fire Department, Oakland Fire Department, FEMA, Alameda County Fire Department, U.S. Forest Service, National Interagency Fire Center, National Wildfire Coordinating Group, U.S. Department of Agriculture, National Weather Service, National Oceanic and Atmospheric Administration, Centers for Disease Control, Pacific Gas & Electric, East Bay Municipal Utility District, East Bay Regional Park District, California Fire Safe Council, Governor’s Office of Emergency Services, Community Emergency Alert Teams, State Council on Developmental Disabilities, University of California Cooperative Extension, Oakland Animal Services, Berkeley Disaster Preparedness Neighborhood Network, Hills Emergency Forum, Alameda County Office of Emergency Services, Berkeley FireSafe Council, Oakland Firesafe Council, Diablo Firesafe Council, FIRESafe Marin, Public Health Institute, California Air Resources Board, Bay Area Air Quality Management District, American Red Cross, Kaiser Permanente, Mask Oakland, Zonehaven, ALERTWildfire, City of Mill Valley, City of Ross.

The image illustrating defensible space in the property section of this guide is adapted from the Wildfire Home Retrofit Guide (publication #SP-20-11) with permission from University of Nevada, Reno Extension and the Living With Fire Program.