Short answer
During dust or smoke events, close windows, run the HVAC fan with the best filter your system can handle (ideally MERV 13 in a media cabinet), turn off fresh-air intakes, and replace the filter afterward. A portable HEPA purifier helps in bedrooms.
During the event
Keep the house sealed and let the filter work.
- Fan set to On, not Auto
- Close outside air dampers and ERV intakes
- Avoid running swamp coolers, which pull in outdoor air
After
Check and replace filters, rinse the outdoor coil once winds calm down, and look at the evaporative cooler pads if you have them.
Upgrades worth considering
Media filter cabinets, sealed returns, and ERVs with good filters all help year after year.
Check the Air Quality Index
AirNow.gov reports the Air Quality Index (AQI) for your area, including smoke and particulate (PM2.5) readings. When AQI is in the unhealthy ranges, keep the house closed and limit outdoor time, especially for children, older adults and people with heart or lung conditions.
Make a clean room
If your system can't take a high-MERV filter, set up one room as a clean room: close its windows and doors, run a portable HEPA air cleaner sized for the room, and avoid frying food, candles or vacuuming without a HEPA vacuum during the event.
Know your filter limits
A filter that is too restrictive for your blower can reduce airflow and cause freezing or overheating. If you want MERV 13, a technician can check static pressure and, if needed, add a deeper media filter cabinet that filters well without choking airflow.
- 1-inch MERV 13 filters can restrict some systems
- 4–5 inch media cabinets usually allow higher MERV with less pressure drop
- Change filters sooner after heavy dust or smoke
Questions
Should I run my swamp cooler during smoke?+
No. Evaporative coolers pull outdoor air in. Switch to AC or recirculation if you have it.
How often should I change my filter after a dust storm?+
Inspect it within a day or two. If it's visibly loaded with dust, change it, even if it's ahead of schedule.
Do HVAC UV lights remove smoke?+
No. UV lights target microbial growth on coils. Smoke particles are removed by filtration, so focus on the filter and a HEPA purifier.
Should I close my outdoor fresh-air intake during smoke?+
Yes, if your system has one. Reopen it once outdoor air quality improves.
Editorial note: this guide is general information for homeowners, not a diagnosis. Desertline Heating & Air is a referral service; a licensed contractor should inspect your equipment before repairs.