Choosing an HVAC Air Filter During Wildfire Smoke

MERV 13 may be useful when supported

MERV 13 is often considered for finer particles, including smoke. Confirm that your system and filter cabinet can use it without creating excessive airflow restriction.

Run the system appropriately

Use recirculation settings when available and avoid drawing outdoor air into the home when outdoor smoke is severe, unless your equipment instructions say otherwise.

Inspect filters frequently

Smoke can load a filter faster than normal conditions. Check the filter during and after a smoke event and replace it when visibly dirty or airflow declines.

Do not rely on one measure

Close gaps, limit indoor particle sources, and consider a properly sized portable air cleaner for occupied rooms. Follow local public-health guidance during smoke events.

Prepare before smoke season

EPA advises using MERV 13 or as high as the HVAC system can accommodate. Confirm compatibility before an event, keep a replacement available, and inspect frequently because heavy smoke can load a filter faster than normal.

Create a cleaner-air room

Choose a room with few openings and use a correctly sized portable air cleaner. Close windows when outdoor air is unhealthy if indoor temperature remains safe, use recirculation where appropriate, and avoid activities that add indoor particles. Health alerts and evacuation guidance always take priority.

A responsible selection process

1. Confirm the nominal and actual dimensions required by the cabinet.
2. Check the equipment manufacturer’s supported filter efficiency.
3. Choose for the household concern rather than the largest number on the shelf.
4. Install the airflow arrow toward the blower or air handler.
5. Inspect the new filter after about 30 days and adjust the schedule to actual loading.

FilterMatch provides an educational starting point, not an HVAC diagnosis. If a filter change causes weak airflow, icing, new noise, or unusual cycling, return to the equipment guidance and consult a qualified technician.

Sources and further reading

FilterMatch checks educational guidance against primary sources. See EPA’s Guide to Air Cleaners in the Home, EPA’s explanation of MERV, and ASHRAE Standard 52.2.

Editorial review: August 26, 2026.