Wildfire smoke guide
How to create a cleaner air room for wildfire smoke.
A cleaner air room is a single room set up to keep smoke and particle levels lower than the rest of the home during wildfire smoke events.
Why it works
Concentrate your clean-air effort in one room.
The US EPA recommends a cleaner air room when wildfire smoke is affecting indoor air and it is safe to remain at home. The idea is simple: reduce smoke entry, continuously remove fine particles, and avoid creating additional indoor pollution.
This can be especially useful when filtering an entire house is difficult, expensive or impossible.
Six-step setup
Build the room before smoke arrives.
Pick a room large enough for the people who will use it. A bedroom can work well, especially if it has an attached bathroom.
Keep windows and doors closed during smoky periods, without blocking a safe exit.
If your air conditioner or HVAC has an outdoor-air or fresh-air setting, close it where appropriate and run in recirculation mode.
Use a correctly sized portable air cleaner, ideally on the highest practical fan speed during a smoke event.
Avoid candles, smoking, vaping, aerosol sprays and high-heat cooking. Vacuum only with a HEPA-filtered vacuum.
When smoke levels outside fall, air out the room and home if conditions allow.
Air cleaner sizing
Size matters more than the HEPA label alone.
EPA guidance says a portable air cleaner should be sized for the room. A useful rule of thumb for wildfire smoke is a tobacco-smoke CADR of at least about two-thirds of the room area in square feet for an 8-foot ceiling. Higher ceilings generally need more CADR.
| Room area | Approx. minimum CADR |
|---|---|
| 100 ft² | 65 cfm |
| 200 ft² | 130 cfm |
| 300 ft² | 195 cfm |
| 400 ft² | 260 cfm |
| 500 ft² | 325 cfm |
HVAC backup
Use MERV 13 if your system can handle it.
For central HVAC, EPA and CDC recommend MERV 13 or the highest efficiency filter your system can accommodate. Continuous fan operation can increase filtration time, but compatibility and airflow matter.
Next steps
Size the air cleaner, then plan its power.
Use the room area and intended fan setting to choose a suitable clean-air delivery rate. If a power outage is possible, estimate the battery runtime for that operating setting. These guides use their own stated assumptions and retain their independent comparisons.
Shopping options for a purifier backup-power plan
Size the air cleaner first, then estimate the energy needed at the fan setting that meets your room’s clean-air requirement. A battery does not make a home safe to occupy or replace evacuation instructions.
Sources
EPA and CDC guidance.
US EPA — How to Create a Cleaner Air Room at Home ↗
US EPA — Indoor Air Filtration ↗
CDC — Wildfire smoke safety guidance ↗
Published 24 September 2026.