Aerial view of wildfire smoke over the San Gabriel Valley

Smoke Ready California

Protecting yourself from wildfire smoke
California is facing increasingly catastrophic wildfire seasons. Wildfire smoke – a complex mixture of air pollutants – is unhealthy to breathe and can be especially dangerous for children, the elderly, pregnant women, and people with heart or respiratory conditions. These sensitive groups are advised to limit outdoor activities, especially when the Air Quality Index (AQI) reaches levels considered ‘Unhealthy for Sensitive Groups’ or above. Even healthy people may experience symptoms in smoky conditions or after exposure. Pets also can be affected by unhealthy air and should be brought indoors, if possible.

California Smoke Spotter

California Smoke Spotter logo
California Smoke Spotter combines advanced smoke forecasting with the latest prescribed fire and wildfire mapping to help you plan your day. Download the app to find out where smoke is coming from, where it’s going, and what it means for your health. Set up personalized alerts, check the AQI, and learn how to protect yourself from smoke.
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    Smoke & Public Health

    California has experienced some of the most destructive wildfire seasons in recent years. Large wildfires often produce intense smoke that can pose serious health risks. There are several steps you can take now to keep your family safe before and during wildfire season.
    Smoke Ready California: Check Local AQI: Check local air quality index levels and listen to local officials. Avoid Breathing Smoke: Smoke can hurt eyes, irritate lungs and worsen chronic heart and lung disease. Use N95 Masks: Use N95 masks marked NIOSH for the best possible protection. MERV 13+ Air Filters: Install a high-efficiency filter with a MERV 13 rating or higher. CARB-Certified Air Cleaners: Using CARB-certified air cleaners can greatly reduce indoor particle levels to further reduce impacts from smoke. Clean Air Space: The best way to avoid wildfire smoke is to stay indoors.

    Air Quality Guide for Particle Pollution

    For the latest information on air quality and smoke near you:
    •    Download California Smoke Spotter.
    •    Visit U.S. EPA’s AirNow Fire and Smoke Map
    •    Check with your air district for local information.

    Air Quality Index: 0-50, Good: Enjoy your usual outdoor activities. 51-100, Moderate: Extremely sensitive children and adults should refrain from strenuous outdoor activities. 101-150, Unhealthy for Sensitive Groups: Sensitive children and adults should limit prolonged outdoor activity. 151-200, Unhealthy: Sensitive groups should avoid outdoor exposure and others should limit prolonged outdoor activity. 201-300, Very Unhealthy: Sensitive groups should stay indoors and others should avoid outdoor activity. 301-500, Hazardous: Everyone should avoid all outdoor exertion. 

    Particulate Matter

    Wildfires produce a range of harmful air pollutants, from cancer-causing substances to tiny particles that can aggravate existing health problems and increase the risk of heart attack or stroke. Particulate matter (PM) is the main pollutant of concern from wildfire smoke for   relatively short-term exposures (hours to weeks). Particles from smoke can be very small (with diameters of 2.5 micrometers and smaller). They are small enough to get deep into the lungs and the tiniest, ultrafine particles can pass directly into the bloodstream. The association between PM2.5 and heart and lung health effects is well documented in scientific literature.

    Larger, more frequent and intense wildfires are a growing public health problem, contributing to reduced air quality for people living near or downwind of fire. Smoke can travel hundreds of miles, so you can be impacted even if you’re not near an active fire. Health problems related to wildfire smoke exposure can be as mild as eye and respiratory tract irritation and as serious as worsening of heart and lung disease, including asthma, and even premature death.

    Wildfire Smoke’s Biggest Health Concern - PM is the most concerning pollutant from short-term exposure to wildfire smoke. Particles can be <2.5 microns (μm) in diameter and can be inhaled into the deepest parts of the lungs causing heart and lung effects. PM2.5: ≤ 2.5 μm, PM10: ≤ 10 μm, Human Hair: 50-70 μm. 


    People who must be outdoors for long periods of time, in areas with heavy smoke, or where ash is disturbed, may want to wear a NIOSH-certified N95 respirator mask. Those with existing respiratory, lung or heart conditions should limit their exposure by staying indoors. Since wearing a respirator can make it harder to breathe, those with lung or heart conditions should check with their doctor before using one.

    If you purchase N95 masks, make sure they are NIOSH-approved. Choose a size and model that fits your face and has no gaps. Test it by doing a seal check

    Wear N95 Masks Correctly: Use an N95 respirator masks marked NIOSH for the best protection against smoke. Place one strap above and one strap below ears (do not cross). Pinch bar to shape of nose. Fits over nose and under chin. NIOSH with N95. Respirator should collapse as you breathe in and not let air in from the sides.

    Some respirator masks are designed and tested to meet international standards, rather than U.S. standards (NIOSH certification). KN95 respirators are the most widely available masks that meet an international standard.

    If you choose to use a KN95 mask, the California Department of Public Health (CDPH) recommends using one that has been tested by NIOSH and has a minimum "filtration efficiency" of 95% or higher. However, it is important to know that while some KN95 models have been tested by NIOSH, they are not designed or approved in accordance with NIOSH standards.

    Almost all KN95s have ear loops, which provide a less-snug fit than respirators with head straps (such as N95s), so it can be difficult to create the seal needed to adequately filter smoke particles. 

    Additional Resources

    Protecting Yourself from Smoke

    Stay Indoors and Keep Indoor Air Clean

    Protect Yourself from Smoke: Check air quality, Close windows & doors, Run AC on recirculate with a new filter, Use a CARB-certified air cleaner, Avoid vacuuming, frying food or using gas-powered appliances, Wear an N95 mask

    The best way to prevent breathing harmful particles in wildfire smoke is to stay indoors.

    • When air quality reaches dangerous levels due to wildfire smoke, the most effective way to reduce exposure and avoid health effects of smoke is to stay indoors with windows and doors closed.
    • If you have a central-ducted air conditioning and heating system, be sure to set the system to “on” to ensure air is being filtered constantly, rather than “auto,” which runs the system intermittently.*
      • If your system brings fresh air into the home, close the fresh-air intake so that it operates in in recirculation mode to prevent outdoor smoke from getting inside.
      • Install a high-efficiency filter (MERV 13 rating or higher) with a MERV rating as high as your system can handle, based on manufacturer recommendations.
    • Consider using a CARB-certified air cleaner which can greatly reduce indoor particle levels to further reduce impacts from smoke.
    • Do not run swamp coolers or whole house fans.
    • Avoid activities that increase indoor pollution, such as burning candles, using gas stoves and vacuuming.

    *In the event of a Flex Alert – a call for consumers to voluntarily conserve electricity when there is a predicted shortage of energy supply, often during heat waves which coincide with wildfire season – follow all guidance from California ISO.

    Use these tips to create a Cleaner Air Space within your home. By focusing on one room or area, cleaning the air becomes more manageable and everyone has a safe place to be during periods of intense wildfire smoke.

    Create a Cleaner Air Space: Choose a room that fits everyone and is comfy enough to spend time in. Close windows and doors, but do not block exits. Filter the air. Use a certified portable air cleaner and run continuously on the highest setting. Avoid activities that create smoke or other particles indoors. Stay cool. Run fans or AC on recirculate with a new filter. Use a damp cloth or mop to trap settled dust and particles.

    Construct a DIY Air Cleaner

    If you don’t have central air or a portable air cleaner to reduce smoke inside your home, another alternative is a do-it-yourself (DIY) air cleaner. These are made with a box fan and MERV 13 air filters.

    DIY Air Cleaner Designs: Good, Better, Best. Materials Needed: 20”x 20” box fan (2012 model or newer), 20”x 20” MERV 13 air filters (1-5 depending on design), Duct tape or bungee cords, Optional: Cardboard for shroud 

    The graphic above shows three popular designs for DIY air cleaners. U.S. EPA researchers tested these designs and found all three are effective at reducing smoke particles. While the cost, supplies and construction of each design are different, there are some important things to keep in mind for all designs:

    • Only use certified box fans marked UL or ETL (2012 model or newer). These have safety features to prevent overheating or an electrical fire if the device is knocked over.
    • Use filters rated MERV 13 or higher. These provide the best filtration.
    • Whenever possible, filters should be mounted to the back of the fan with the arrow printed on the filter pointing toward the fan (in the same direction as the airflow). Avoid using fans that have motor housings or power cords on the back that will keep a filter from fitting tightly against the back of the fan with no gaps.
    • Replace filters when they are dirty or develop an odor. U.S. EPA’s research found that DIY air cleaners were almost completely ineffective with dirty filters.
    • Keep extra filters on hand so you don’t have to go out during a smoke event for replacements.

    Ways to improve effectiveness

    • Add a carboard shroud, as seen in the designs above.
    • Use thicker filters (4-inch, rather than 1-inch MERV 13 filters)

    While all three models represented here will clean the air in your home, EPA’s research shows that models with more filters are more effective at removing smoke particles from the air.  

    DesignSmoke FiltrationSupplies NeededAverage Cost of Materials*


    (1 filter)

    • 20” x 20” box fan
    • One 20” x 20” MERV 13 air filter
    • 20” x 20” cardboard shroud (cutout the size of the fan blades)
    • Duct tape, bungee cords, or clamps


    (2 filters)

    • 20” x 20” box fan
    • Two MERV 13 air filters
    • 20” x 20” cardboard shroud (cutout the size of the fan blades)
    • Cardboard triangle cut to cover top of device between the filters and fan
    • Duct tape, bungee cords, or clamps

    Corsi-Rosenthal Box

    (4-5 filters)

    • 20” x 20” box fan
    • Four or five 20” x 20” MERV 13 air filter (bottom filter can be replaced with a 20” x 20” piece of cardboard)
    • 20” x 20” cardboard shroud (cutout the size of the fan blades)
    • Duct tape, bungee cords, or clamps
    • Leg supports (ie. blocks) if using 5-filter design (to allow airflow through bottom)

    *Prices obtained for U.S. EPA research from national retailers in April 2022; filter unit price derived from a pack of six filters (See study Section 3.2, Table 2)

    Instructional Videos

    Clean Air Centers

    If cleaning the air inside your home is not possible, contact your local Air Pollution Control District or local officials to see if a designated Clean Air Center is open in your community. This could be a recreation center, library, school gymnasium, or other indoor facility equipped with proper ventilation and air conditioning that is open to the public during smoke events.

    Avoid outdoor activities

    Keeping Children Safe from Smoke: Things you can do - Check with local air districts. Move event indoors. Postpone event. Move event to cleaner air.
    • People should avoid exercising outdoors during smoky conditions. Exposure and the resulting health effects depend on the amount of time spent outside, level of exertion, level of air pollution, and possible existing health conditions.
    • Consider eliminating outdoor activities altogether when the AQI reaches unhealthy levels.
    • Officials may call for an evacuation in emergency situations or when the AQI reaches hazardous levels. Always follow evacuation orders. In the event of an evacuation, make sure to operate your vehicle with the windows rolled up and the air conditioner set to recirculate.

    Evacuation Smoke Safety

    Keeping Children Safe from Smoke: Things you can do - Check with local air districts. Move event indoors. Postpone event. Move event to cleaner air.

    It’s easy to forget about smoke when evacuating from wildfires. There are several easy ways to protect yourself when traveling to an area with better air quality. 

    • Stay inside your vehicle with windows and doors closed.
    • Run the air conditioning with Recirculate turned on.
    • Wear an N95 mask in your vehicle and at shelters.
    • For those with asthma or respiratory conditions, bring inhalers and medication.
    • Try to evacuate to an area with better air quality.
    • Always follow evacuation orders.