If you live in California, wildfire smoke is no longer a once-in-a-decade event. The 2018 Camp Fire, the 2020 North Complex, the 2021 Caldor, the 2023 Park Fire, and the 2025 Palisades and Eaton fires have all pushed enormous quantities of fine particulate matter into homes across the state — even homes hundreds of miles from the actual flames.
Most of that smoke didn't just wash out when the air cleared. A significant portion of it settled inside your home's ductwork, where it now recirculates through your HVAC every time the system runs.
This guide walks you through what's actually happening inside your ducts after a fire, why it matters for your health, and what professional air duct cleaning in California involves.
What wildfire smoke actually does to your HVAC system
Wildfire smoke is fundamentally different from ordinary household dust. It contains PM2.5 — particulate matter smaller than 2.5 micrometers across. For context, a single human hair is about 70 micrometers thick. PM2.5 particles are roughly 30 times smaller.
Because they're so small, PM2.5 particles bypass your HVAC system's standard filter and accumulate inside the ductwork itself — on the metal walls, in the seams, in the flex-duct bends, and in the return registers. Once deposited, they sit there.
Every time your HVAC turns on, air rushes past these deposits and dislodges some of them, sending fresh particulate into the rooms of your home. This is why many California homeowners report a persistent "smoke smell" indoors for months after the fires are out — even with windows closed, even after a deep cleaning of surfaces.
"After the 2025 Palisades fire we kept smelling smoke inside, even with windows shut. The ash buildup in the ductwork was real — and once it was cleaned, the difference was immediate." — California Airduct Pros customer (Pasadena)
The health risk most homeowners underestimate
PM2.5 from wildfire smoke is classified by the EPA as a serious health hazard. It's small enough to penetrate deep into the lungs and even enter the bloodstream. Long-term exposure is linked to:
- Cardiovascular disease — heart attacks, strokes, hypertension
- Respiratory illness — worsened asthma, COPD, bronchitis
- Reduced lung function in children
- Increased mortality in elderly populations
You can check your current outdoor air quality at any time at AirNow.gov. But what AirNow can't tell you is what's still sitting inside your home's ductwork, recirculating every time the AC clicks on.
Step-by-step: what California homeowners should do after a fire
1. Don't run your HVAC during heavy smoke days
If the AQI is above 150, switch your HVAC to "off" or set the fan to "Auto" rather than "On". Running it during the smoke event pulls more smoke into the ductwork. If you must filter air, use a portable HEPA air purifier in your bedroom instead.
2. Replace your filter immediately after smoke clears
Your standard HVAC filter caught some of the larger particles, but it's now saturated and will release them slowly. Replace with a MERV-13 or higher rated filter (the highest your system can handle without restricting airflow).
3. Schedule a professional inspection
A experienced technician will use a camera scope to inspect the actual condition of your ductwork. They'll show you photos of what's inside — and recommend cleaning only if needed. A reputable company won't pressure you into a cleaning if your ducts are clean.
4. Professional HEPA negative-air cleaning (if recommended)
Professional post-fire cleaning uses commercial negative-air machines equipped with HEPA filtration. The machine creates a vacuum across your entire duct system, pulling all loosened particulate into a sealed container — not back into your home.
A experienced crew will:
- Seal supply and return registers
- Set up the HEPA negative-air machine at the air handler
- Insert mechanical brushes and air-whips through each duct line
- Agitate deposits while the negative-air machine captures everything
- Clean the air handler coils, blower, and plenum
- Apply EPA-registered antimicrobial treatment (optional but recommended after smoke exposure)
- Document the work with before/after photos at every duct opening
The full process takes 3-5 hours for a typical California single-family home.
Were you affected by California wildfires?
California Airduct Pros has cleaned hundreds of homes affected by Palisades, Eaton, Sunset, Hughes, and earlier fires. Free in-home inspections statewide. experienced technicians. No upsell.
Get Free California Estimate →What this costs in California
Post-fire air duct cleaning cost varies significantly based on smoke exposure severity, home size, number of vents, and whether antimicrobial treatment is needed. Because of this, California Airduct Pros doesn't quote post-fire cleaning prices over the phone — every wildfire-affected home is different.
What we do instead: provide a free in-home camera-scope inspection. The technician documents what's actually inside your ducts after the smoke event and provides a written itemized quote on the spot. Most of our wildfire-recovery jobs start exactly this way.
What we can tell you about the industry: legitimate professional cleaning is labor-intensive (3-5 hours, two technicians, commercial HEPA equipment) and is significantly cheaper than replacing damaged HVAC components, treating ongoing respiratory illness, or repainting smoke-stained walls. Be wary of $99 specials advertising post-fire service — they cannot deliver real cleaning at that price.
Don't wait for the next fire
California's wildfire seasons are getting longer, not shorter. If you weren't directly affected by the most recent fire but live within 100 miles of one, your home likely received smoke. A camera inspection costs nothing and tells you exactly what's inside.
If you're in Los Angeles, the Bay Area, San Diego, Sacramento, or anywhere else in California, California Airduct Pros provides free in-home inspections statewide.