Keeping Wildfire Smoke Out of Your Home

Filters and settings for smoky days.

Updated October 27, 2026

Use a better filter

The EPA and ASHRAE both point to filters rated MERV 13 or higher for removing smoke particles from indoor air. Many homes have a thin 1-inch filter rack that was meant for cheap filters. A thick MERV 13 filter can choke airflow in that kind of slot.

• Check what your system can handle before you switch
• A 4- or 5-inch media cabinet allows high MERV with less restriction
• Change filters more often while the smoke lasts
• Keep a spare on hand before fire season starts

Settings for smoky days

1. Close windows and doors and keep them shut.
2. If your system has a fresh air intake, close it or set it to recirculate. The EPA recommends this during smoke events.
3. Set the thermostat fan to On so air keeps passing through the filter even when the AC is not cooling.
4. Ductless mini-splits have only a light screen filter. Pair them with a portable HEPA air cleaner in the rooms you use most.

Smoke and heat at the same time

The worst days stack smoke on top of heat. Homes with no AC face a hard choice between opening windows and letting smoke in, or staying shut and baking. A heat pump or mini-split lets you keep the house sealed and cool at once. The guide to adding AC covers the options.

Questions about Wildfire smoke and your HVAC in Gresham

Will a MERV 13 filter hurt my system?

It can, if the system was not built for it. A thick filter in a thin slot restricts airflow and can freeze the coil. A contractor can check static pressure and suggest a media cabinet.

Should I run my AC when it is smoky?

Yes, with windows shut and the fresh air intake closed. The AC recirculates indoor air through the filter.