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Filtration, smoke and ash, and clean ducts
Indoor Air Quality in Los Angeles: Smoke, Ash and Your HVAC
Since the January 2025 Palisades and Eaton fires, a lot of LA homeowners have asked the same question: is the air inside my house actually clean? Your heating and cooling system can either help a lot or quietly spread smoke and ash around. Here is how to make it help.
- Filter upgrades matched to what your system can handle
- Coil and blower cleaning after smoke and ash events
- No ozone gimmicks: only air cleaners that are legal and proven
Quick filter guide
- MERV 8 Everyday dust and pollen
- MERV 11 Better for pets and allergies
- MERV 13 Catches most smoke particles
- HEPA Portable purifiers, most rooms
Check that your system can handle a higher MERV filter before you switch. A filter that is too restrictive can freeze the coil.
The short answer
Does My AC Filter Wildfire Smoke?
Only if it has the right filter and the fan is running. Standard 1-inch filters (often MERV 4 to 8) catch dust and pollen but let most fine smoke particles through. A MERV 13 filter catches a large share of them, which is why it is the level the EPA points to for wildfire smoke.
The catch is airflow. Thicker, finer filters can restrict airflow on older or undersized systems, which can freeze the evaporator coil and cut cooling. A deeper 4 to 5 inch media filter cabinet solves that for most homes because it gives the air more surface area to pass through.
During smoke
What to Do With Your HVAC During a Smoke Event
- Keep windows and doors closed and run the system on recirculate.
- Close any outdoor air intake or fresh-air damper, and turn off whole-house fans and evaporative (swamp) coolers, which pull outside air in.
- Run the fan with a MERV 13 filter installed, so the air keeps passing through the filter.
- Use a portable HEPA purifier in the bedroom. It is the single cleanest room you can create.
- Check the filter after the event. Smoke and ash can load a filter fast. Replace it if it has darkened.
- Watch the air quality. South Coast AQMD posts local air quality and smoke advisories for LA County.
After the fires
Smoke and Ash in Your AC After a Fire
Ash and soot do not just affect the air you breathe. They also land on the outdoor coil, get pulled into the return, and coat the blower and indoor coil. We still see the effects in homes near the Palisades and Eaton burn areas.
- Outdoor coil packed with ash. It raises pressures, makes the system work harder and pushes up your bill. A proper coil cleaning fixes it.
- Lingering smoke smell when the AC runs, usually from soot in the ducts, the blower wheel or the coil.
- Filters that clog in days instead of months.
- Ash in the ductwork, especially where there were gaps or the system was running during the fire.
Not every home needs duct cleaning. But if you see soot at the registers, smell smoke when the system starts, or your home was close to a burn area, a duct inspection is worth it. See ductwork.
Choosing equipment
Air Cleaners: What Works and What to Avoid
| Option | Good for | Watch out for |
|---|---|---|
| MERV 13 filter (1 inch) | Simple, cheap smoke upgrade | Can restrict airflow on some systems |
| 4 to 5 inch media filter cabinet | Whole-home filtration with less airflow loss | Needs installation in the return |
| Portable HEPA purifier | Bedrooms and smoke events | Size it to the room; replace filters |
| Ozone generators and “ionizers” that make ozone | Nothing worth the risk | Ozone irritates the lungs. California regulates air cleaners for ozone, so look for CARB certification. |
The California Air Resources Board (CARB) requires air cleaning devices sold in the state to meet an ozone emission limit. If a product promises to “shock” your home clean with ozone, skip it.
Every day
Everyday Air Quality Problems We See in LA Homes
- Dust from leaky attic ducts. Return leaks in a hot attic pull insulation dust and attic air into the house.
- Musty smells from mold on a mini-split blower wheel or in a damp drain pan.
- Dry air during Santa Ana wind events.
- Allergy seasons that never fully end in Southern California.
FAQ
Frequently Asked Questions
What filter is best for wildfire smoke?
A MERV 13 filter catches most fine smoke particles and is the level the EPA points to for wildfire smoke. Check that your system can handle it, or add a deeper media filter cabinet so airflow is not restricted.
Should I run my AC during wildfire smoke?
Yes, on recirculate, with windows closed, any fresh-air intake shut and a good filter installed. Turn off swamp coolers and whole-house fans, which pull smoky air inside.
Do I need duct cleaning after a wildfire?
Not always. If you see soot at the registers, smell smoke when the system runs, or your home was close to a burn area, have the ducts, blower and coil inspected first.
Are ionizers and ozone air purifiers safe?
Avoid devices that make ozone. It irritates the lungs. California requires air cleaners sold in the state to meet CARB’s ozone limit, so look for CARB certification.
Why does my AC smell like smoke?
Usually soot or ash in the filter, coil, blower or ducts from a past smoke event. A new filter helps. A lasting smell needs cleaning of the parts holding the soot.
Related
Related Services and Guides
AC maintenance
Coil cleaning and filter checks every spring.
Ductwork
Sealing, repair and cleaning for attic ducts.
Ductless mini-splits
Deep cleaning for musty mini-split heads.
Heating and furnaces
Cleaner air during winter, when windows stay shut.
Want cleaner air at home?
Call for filter upgrades, coil cleaning or a smoke and ash inspection of your system, anywhere in the Valley or Central LA.
Last updated October 2026. Prices are published 2026 Los Angeles market ranges, not quotes. Rules and rebates change, so check the official source before you buy.