The short answer
When wildfire smoke or particle pollution is affecting your area, close exterior openings in one safe occupied room, stop adding particles indoors, and use compatible filtration if you have it. Keep checking the room temperature, smoke entry, power, official instructions, and the people inside. Leave for a cooler or cleaner location if the room cannot remain safe.
Start here
- Confirm that wildfire smoke or particle pollution is the problem. A high AQI can also be driven by ozone or another pollutant.
- Choose one occupied room that can close, stay cool, fit the people and animals using it, and keep an exit clear.
- Close the room's exterior windows and doors, then limit exhaust fans when doing so will not interfere with required ventilation or appliance safety.
- Stop smoking, vaping, burning candles or incense, using aerosols, frying or broiling food, and vacuuming without a HEPA filter.
Confirm that particles are the problem
Use this procedure when the primary pollutant is PM2.5 or PM10, or when an official source identifies smoke in the area. Read the AQI number together with the pollutant, place, and update time.
Particle filters do not remove every gas, and they do not make a room safe from carbon monoxide. If officials tell your area to evacuate, leave according to those instructions.
Reduce outdoor air entering the room
Close the room's windows and exterior doors while keeping normal exits usable. Limit range hoods, bathroom fans, and other exhaust fans when they would pull smoky outdoor air inside, but do not defeat required ventilation, a combustion-safety control, or an appliance's instructions.
Use a recirculation setting only when the heating or cooling system is designed for it. A single-hose portable air conditioner can pull outdoor air into the building, so use another safe cooling option during smoke when one is available.
Stop producing particles indoors
- Avoid smoking, vaping, candles, incense, and aerosol sprays.
- Avoid frying and broiling food when another practical meal is available.
- Do not use wood, gas, or propane equipment that is not safely vented.
- Use a damp cloth or mop for settled dust. Avoid vacuuming unless the vacuum has a HEPA filter.
Use filtration already available
Use the highest-efficiency filter the system can accommodate. EPA recommends MERV 13 when compatible. Check the equipment instructions or ask a qualified technician when compatibility is uncertain.
Use a unit sized for the room by its smoke clean air delivery rate. Run it on the highest tolerable setting and choose equipment that does not intentionally produce ozone.
Closing exterior openings, reducing indoor particle sources, and spending more time in one suitable room can still reduce exposure. Buying an appliance is not the first step.
If you use a temporary box-fan filter
A do-it-yourself box-fan filter can reduce particles when a commercial cleaner is unavailable or unaffordable. Use a newer box fan made in 2012 or later with a UL or ETL safety marking and a MERV 13 filter, or the highest-efficiency filter available.
- Attach the filter to the air-intake side with its airflow arrow pointing toward the fan, then seal the edges so most air passes through the filter.
- Keep the fan stable and clear of curtains, water, and walkways. Plug it directly into a wall outlet.
- Do not use a damaged fan or cord. Do not use an older fan unattended or while anyone is asleep.
- Replace the filter when it is visibly dirty or smells strongly of smoke.
Check the room and know when to leave
Keep checking official instructions, the current outdoor particle AQI, room temperature, visible or noticeable smoke entry, filter condition, power, and how each person and animal is doing. When outdoor particle levels improve, air out the home only if doing so will not introduce another hazard.
- Leave if emergency authorities tell the household to evacuate.
- Use another location if the building becomes too hot or too much smoke keeps entering.
- Leave if a power outage prevents safe cooling or needed medical equipment from operating.
- Leave and follow emergency guidance if a carbon monoxide alarm sounds.
- Follow an individual care plan or seek medical help when symptoms require it.
What changes this answer
General guidance becomes a personal decision through these details.
Particle pollution responds to filtration. Ozone, carbon monoxide, chemical releases, and other hazards require different instructions.
Exterior openings, safe temperature, usable exits, capacity, access needs, and nearby facilities change whether it works.
Filter compatibility, room sizing, cooling, power, fan condition, and manufacturer instructions set the safe operating boundary.
Children, older adults, animals, symptoms, care plans, medical equipment, and the ability to reach another location change the decision.
Where this guidance stops
- No household room or air cleaner removes every pollutant or makes a home safe from an approaching fire.
- Do not close a home so tightly that it overheats or interferes with required appliance ventilation.
- This guide does not replace evacuation instructions, a carbon monoxide alarm, an individual medical plan, or current advice from public-health and emergency authorities.
Sources
Consequential guidance is checked against the linked source material.
- U.S. Environmental Protection Agency. Create a Clean Room to Protect Indoor Air Quality During a Wildfire. Updated August 18, 2026. Checked August 28, 2026.
- U.S. Environmental Protection Agency. Research on DIY Air Cleaners to Reduce Wildfire Smoke Indoors. Updated July 6, 2026. Checked August 28, 2026.
- U.S. Environmental Protection Agency. Guide to Air Cleaners in the Home. Portable and central filtration guidance. Checked August 28, 2026.
- U.S. Environmental Protection Agency. Indoor Air Filtration. Filter selection and use during wildfire smoke. Checked August 28, 2026.
- AirNow. Air Quality Guide for Particle Pollution. EPA-452/F-23-002, February 2023. Checked August 28, 2026.
General information, not advice tailored to you or a guarantee of safety. You are responsible for decisions about your safety. Follow current directions from local authorities. Read the safety disclaimer.