Start with one room and enough particle filtration. During wildfire smoke, choose a room you can keep closed and comfortably cool, then match the air cleaner's smoke CADR to that room. Buying the largest advertised “coverage” number can be misleading.
Set up a cleaner-air room
EPA recommends a room large enough for the people using it, with few windows and doors and room for the air cleaner. Keep outside windows and doors closed without obstructing an exit. Use the appropriate recirculation settings for your ventilation system and follow the equipment instructions. A window air conditioner, evaporative cooler and central system do not all handle outdoor air the same way.
Run the purifier continuously at the highest setting you can tolerate. Keep its air intake and outlet clear. Avoid creating more indoor particles through candles, smoking, frying or other smoky activities. A quiet sleep setting may be comfortable, but it generally moves less air than the setting used for the published CADR.
Use your room dimensions when comparing smoke CADR. This photograph illustrates room planning, not a tested cleaner-air setup.
Open the room-sizing calculator Photo: Minh Pham / UnsplashUse smoke CADR as the starting point
CADR is clean air delivery rate, usually expressed in cubic feet per minute. EPA's minimum sizing rule is a smoke CADR at least two-thirds of the room's area in square feet. Higher ceilings, open connections to other rooms, heavy infiltration and lower fan settings can call for more capacity. This is a minimum planning rule, not a promise of a particular indoor pollution level.
| Room area | Minimum smoke CADR | Calculation |
|---|---|---|
| 150 sq ft | 100 cfm | 150 × 2/3 |
| 300 sq ft | 200 cfm | 300 × 2/3 |
| 450 sq ft | 300 cfm | 450 × 2/3 |
| 600 sq ft | 400 cfm | 600 × 2/3 |
Look for the smoke CADR on the model's label or certification information. Dust, pollen and a general CADR listing are not automatically identical. Compare units using the same metric and fan setting.
Two larger-room options to investigate
| Option | Manufacturer's airflow figure | What to check before buying |
|---|---|---|
| Coway Airmega 400 | 328 cfm smoke CADR | Exact-model certification, filter-set cost, noise on the setting you will use. |
| Levoit Core 600S-P | 391 cfm general CADR; product page does not separately label smoke CADR | Confirm the smoke-specific figure. Its 606 sq ft figure is stated at 4.8 air changes/hour. |
We use Coway's published smoke figure here rather than treating its one-air-change coverage claim as the area protected during wildfire smoke. Levoit's general CADR is included transparently, not relabeled as a smoke rating. These are research-based candidates for a larger-room comparison; this is not a head-to-head smoke test.
Compare ongoing filter costs as well as the device. Check replacement-filter availability, how pre-filters are cleaned, the exact filter model, and whether the controls let you hold a steady fan setting. A larger purifier may offer useful airflow headroom, but a smaller correctly specified unit can be enough for a smaller closed room.
Know what filtration cannot do
EPA favors mechanical particle filtration and warns against ozone-generating equipment. Verify the exact model's emissions information; an emissions certification does not establish that its airflow is large enough for your room. HEPA or pleated filters target particles. Do not assume an odor-reduction carbon layer removes all wildfire gases, and never use a purifier as a substitute for a carbon-monoxide alarm.
If buying a commercial unit is not feasible, EPA also discusses DIY air-cleaner options and their precautions. Follow its current guidance rather than improvising with damaged fans, obstructed airflow or unsupported electrical arrangements.
A purifier also needs power. If you intend to run one from a battery, include its actual power use at the desired fan speed in your backup energy plan. An outage plus smoke plus heat can make staying home impractical even with equipment.
Next: see the indoor-air preparedness hub and include a clean-air destination in your longer-disruption plan.