Wildfire smoke at home

Why smoke matters

Wildfire smoke is dominated by fine particles (PM2.5) small enough to travel deep into the lungs. It is especially hard on children, older adults, pregnant people and anyone with asthma, COPD or heart disease. Smoke also travels hundreds of miles, so a clear sky can still carry it.

Before the season

• Choose a clean room—usually a bedroom—with few windows and a door that closes.
• Buy a HEPA purifier with a smoke CADR suited to that room, and spare filters.
• If you have central air, buy MERV 13 filters (or the highest your system supports).
• Bookmark AirNow for local readings.

During a smoke event

• Keep windows and doors closed; set the HVAC fan to recirculate and turn off fresh-air intakes.
• Avoid frying, candles, incense, gas stoves where possible and vacuuming without a HEPA filter.
• Run the purifier continuously on a speed you can tolerate; higher speeds matter more than usual.
• Watch indoor PM2.5 if you have a monitor; it shows whether your clean room is working.
• In hot weather, do not let the home overheat to keep smoke out—heat is also a health risk.

A budget option

A box fan with a MERV 13 filter attached (sometimes called a Corsi–Rosenthal box when built from four filters) is a well-studied, inexpensive stopgap. Supervise it and do not leave it running unattended.

After the smoke clears

Air the home out once outdoor readings improve, replace loaded filters, and wipe surfaces where ash settled.