Wildfire smoke: how to protect yourself, your home and your family

Wildfire smoke is a mix of gases and fine particles from burning trees, grass and buildings. The particles are the main danger. Most are smaller than 2.5 micrometres (PM2.5), small enough to reach deep into the lungs and the bloodstream. Smoke can travel hundreds or even thousands of miles, so you don't need to be near a fire to be affected.

This guide is for the US, where the EPA's AirNow network and the National Weather Service track smoke, but the advice applies anywhere.

Fire season is not over

Fire activity in the US has shifted south as autumn arrives. In Southern California, the Bouquet Fire in the Angeles National Forest started on 3 October 2026 and had burned 1,048 acres by 5 October, when it was 48 percent contained. Smaller fires have followed, including one near Santa Clarita that forced evacuations on 11 October (Latin Times, 12 October).

Track it live: where US air is worst right now and active National Weather Service alerts.

Read the AQI, not the sky

Smoke can look thick while the air at ground level is fine, and the reverse. Check the Air Quality Index from the monitor nearest you, ideally the hourly reading:

More detail for each range: AQI 101 to 150, 151 to 200, 201 to 300.

Masks that work against smoke

• Use an N95 or KN95 respirator (FFP2 in Europe). It filters at least 95 percent of fine particles, but only if it seals: no gaps at the nose or cheeks, and it won't seal over a beard.
• Cloth masks, surgical masks and bandanas don't protect against smoke particles.
• No mask filters the gases in smoke, such as carbon monoxide. The safest move is still to reduce time outside.
• Children's masks need to fit their faces; ill-fitting adult masks give little protection.

Make a clean room at home

Smoke gets indoors through gaps and ventilation. Pick one room, ideally a bedroom with few windows, and:

1. Close windows and doors. Seal obvious gaps with tape or towels if smoke is heavy.
2. Run a portable HEPA air purifier sized for the room. Look for a clean air delivery rate (CADR) in square feet of at least two thirds of the room's floor area.
3. No purifier? A box fan with a MERV 13 furnace filter taped to its back makes an effective low-cost filter. The four-filter "Corsi-Rosenthal box" works even better. Never leave a homemade fan filter running unattended.
4. Set central air to recirculate and use the best filter your system takes, MERV 13 if possible. Turn off swamp coolers and whole-house fans, which pull smoke in.
5. Don't add indoor pollution: avoid frying, candles, incense, gas stoves without a hood, smoking and vacuuming, which stirs up dust.

In the car

Close the windows and set the air to recirculate. Car cabin filters help a little; some newer cars have HEPA-grade filters.

Children, pets and people at higher risk

• Children breathe more air for their size and spend more time outside, so they get a bigger dose. Move recess, practice and play indoors when the AQI is above 150, or above 100 for children with asthma.
• People with asthma, COPD or heart disease should have their medicines and an action plan ready, and seek care for chest pain, severe breathlessness or an irregular heartbeat.
• Pregnant people should limit exposure too; studies link smoke exposure to lower birth weight.
• Pets: keep walks short and bring outdoor animals in.

After the smoke clears

Ash on surfaces can contain irritants and metals. Wet it down before cleaning, wear gloves and an N95, and avoid leaf blowers that put it back in the air. Replace HVAC and purifier filters after a heavy smoke event.