How to prepare for wildfire smoke in your home, car and while outdoors

Wildfires that choked the region with smoke in recent summers show no sign of abating amid the worsening effects of a changing climate. Here’s how to minimize your exposure to smoke from such fires, which can irritate the lungs, cause inflammation, impair immune function and increase susceptibility to respiratory infections. Children, adults over the age of 65, pregnant people, outdoor workers, those with chronic health conditions, who are homeless or who have limited access to medical care are particularly vulnerable.

During smoky weather

Stay inside with doors and windows closed. Run air conditioning where available. If your HVAC (heating, ventilation and air conditioning) system or window air conditioner has a fresh-air intake option, turn it off or close the intake. Consult a HVAC professional for further instructions. Set a reminder to reset your system once the smoke clears. Older leaky homes without air conditioning provide less protection. Seek shelter elsewhere if it’s too warm to keep the windows closed.

Reduce physical activity and avoid strenuous work and outdoor exercise as heavy breathing can push pollution deeper into the lungs. Stay hydrated. If you develop symptoms suggesting lung or heart problems, consult a health care provider as soon as possible.

Be alert to local advisories, air quality forecasts and changing smoke conditions. Visit fire.airnow.gov for the latest reports.

Preparing a clean air room

Creating a “clean room” can make it easier to manage indoor air quality on a smaller scale. Here’s how:

1. Choose a room that can comfortably fit everyone in your household.
2. Keep doors and windows closed, but don’t impede your exit.
3. Set up a portable high efficiency particulate air (HEPA) cleaner appropriate to the size of the room. Look for one that cycles the air several times per hour, but does not emit ozone or use ionization technologies. Units are labeled for their Clean Air Delivery Rate. Select options that have a CADR equal to or greater than the size of the room where they’ll be used.
4. Use a damp mop or rag to clean to avoid sending particles back into the air. Don’t vacuum unless using one with a HEPA filter.

Stock up on food and other supplies so you don’t need to go out in the smoke. Have a supply of medication and nonperishable groceries that don’t require cooking.

Minimize activities that could generate particles indoors. Don’t smoke, use aerosol products, burn candles or incense or use gas, propane or wood-burning stoves.

Smoke may still enter your home even if you take these steps. When outdoor air quality improves, open windows to ventilate and reduce indoor air pollution.

Building your own air cleaner

Your air cleaner doesn’t need to be expensive to be effective. You can build your own using a box fan, a furnace filter and masking tape. Use a 20-by-20 inch box fan and a filter of the same size, either a MERV 13 or FPR 10 filter. Research by the Puget Sound Clean Air Agency found that a box fan filter can lead to a 90% reduction in certain types of air pollution.

Using one filter

Use tape to attach the filter to the back of the fan, making sure the arrow on the filter follows the direction of airflow.

Using two filters

You can make a double filter cleaner that puts less strain on the fan with the addition of another filter and two 21-inch cardboard triangles. Place the two filters side by side with the arrows the same direction and tape them together, forming a hinge. Tape the sides of the filters to the fan, making sure the arrows point toward the direction of airflow. Then tape one cardboard triangle to the top and another to the bottom of the filters.

Never leave the filter fan running while sleeping or when not at home. Remove the filter before sleep if airflow is important to stay cool. Turn off the filter fan every 30 minutes and allow the unit to cool off for 15 minutes before turning it back on.

Box fans were not designed to be used with furnace filters and while there is no data to show that overheating has been a problem, no formal testing has been conducted and the risk of overheating remains possible.

Using a respirator

Respirator masks can be effective at reducing exposure to smoke particles, but they should only be used after implementing other, more effective methods of exposure reduction such as staying indoors, reducing activity and using a HEPA air cleaner.

NIOSH N95 or P100 masks, when worn correctly, filter small particles and improve the quality of air being inhaled. The mask must form a tight seal around the wearer’s mouth and nose to work. They are not designed to fit children.

Look for masks with two straps that go above and below the ears.

One-strap paper masks, surgical masks, or other face coverings do not offer smoke protection.

Masks can be purchased online or at hardware stores.

Those with respiratory or heart conditions should consult their health care professional before wearing a respirator mask.

Car safety

Use your car to get to a clean-air shelter, but not as a primary retreat.

Turn off the ventilation system and keep windows shut, or ensure vehicles are equipped with a HEPA cabin air filter ahead of a smoke event.

Do not run the air conditioning using the recirculation setting with windows closed. Recent research has shown that carbon dioxide can accumulate at high levels in newer cars with vents and windows closed when using the recirculation setting for extended periods of time.

Drive carefully in smoky conditions.

Never leave children or pets alone in a vehicle with the windows closed.

Public clean air spaces

Seek shelter elsewhere if you or your family are particularly at risk and do not have adequate filtration or cooling at home. Temporary respite can be found at libraries, museums, malls, senior centers and other indoor facilities with effective particle filtration and cooling. Verify sites are properly equipped with MERV 13 filtration or higher before venturing out into the smoke.

Follow current local COVID-19 precautions as directed.

Sources: California Air Resources Board, California Office of Environmental Health Hazard Assessment, U.S. Centers for Disease Control and Prevention, U.S. Forest Service, U.S. Environmental Protection Agency, King County Public Health, Colville Confederated Tribes Air Quality Program