Wildfire smoke contains fine particles that can enter buildings. A portable air cleaner may reduce particles in a room when selected and used as directed, but no consumer unit removes every pollutant or guarantees a particular indoor concentration. Follow local public-health and emergency guidance.
For related room planning, see our home climate and indoor air resilience guide.
CADR Mathematics & Air Changes Per Hour (ACH)
Clean Air Delivery Rate (CADR) is a product rating for particle-cleaning performance. EPA advises choosing a portable air cleaner with a smoke CADR of at least two-thirds of the room’s floor area in square feet. EPA’s table gives 195 CFM for a 300-square-foot room with an 8-foot ceiling; for higher ceilings, choose a higher CADR. Room layout and use also affect performance.
Use the manufacturer’s stated room size and smoke CADR when comparing models. A volume-based air-change calculation can be used as a planning estimate only when the assumptions are explicit; EPA’s cited guidance does not require five air changes per hour or a particular H13 filter class. Do not present a calculated rating as a guaranteed particle reduction.
Wildfire Air Filtration Decision Matrix
| Option | What to check | Limits and cautions |
|---|---|---|
| Portable air cleaner | Smoke CADR and stated room size; EPA suggests smoke CADR at least two-thirds of floor area, with more for higher ceilings | Follow the product label and instructions. CADR does not establish removal of gases or every pollutant. |
| Central HVAC filter | MERV 13 or the highest-efficiency filter the system supports; check the equipment manual or consult a technician | A filter unsuitable for the system can affect airflow; do not assume a universal compatible rating. |
| Gas-phase filter media | Product-specific information about the named gases and expected performance | Carbon media may reduce some gases; particle CADR does not rate gas removal. |
| Electronic air cleaner / ionizer | EPA guidance on ozone-generating devices and product-specific documentation | Avoid devices that intentionally generate ozone; ozone can harm health. |
Fan Speed & Acoustic Load Trade-offs
Check the manufacturer’s CADR and noise information for each operating speed. A rating may be reported at the highest setting, which can be louder than a lower setting. Compare the ratings for the speed you can realistically use, especially in a sleeping area; there is no single noise or CADR value common to all products.
Acoustic and Airflow Optimization Table
| Check | What to compare |
|---|---|
| Cleaning performance | Smoke CADR or room size stated for the product and operating speed, where provided |
| Noise | Product’s sound rating at settings you expect to use |
| Ongoing use | Filter availability, replacement directions, and the cost and frequency stated by the manufacturer |
Clean Air Room CADR Worksheet
- Measure the room’s floor area and note ceiling height. For a portable cleaner, compare those dimensions with the EPA room-size guidance and the product’s smoke CADR; choose a higher CADR for a higher ceiling.
- Place and operate the unit as its instructions specify. Keep doors and windows closed during smoke when public-health guidance says it is appropriate, and follow local alerts.
- Reduce indoor particle sources where practical, such as smoke from cooking, candles, or tobacco. Do not disable required ventilation or combustion-safety equipment; consult qualified professionals when needed.
- Check and replace or clean filters as directed by the manufacturer. If a consumer particle monitor is used, treat it as an indicator rather than a health guarantee.
EPA’s guidance does not mandate H13, five ACH, a PM2.5 threshold, or a guaranteed protection level. Air cleaning can complement other steps but cannot eliminate all exposure. Follow official guidance, including instructions to relocate when conditions require it.
