By Carl Gibbons, Lead Inspector, A-1 Certified Environmental Services
Possibly, yes — and the reason surprises most people.
After the January 2025 Los Angeles fires, air quality testing researchers measured indoor and outdoor air at two dozen locations near the Palisades and Eaton burn areas. During the recovery phase, homes inside the burn zones showed higher indoor concentrations of benzene, toluene, ethylbenzene and xylene than the outdoor air, likely from smoke-impacted materials off-gassing indoors. The researchers noted the practical risk directly: residents may feel safe returning home once the fires are out, while still being exposed to lingering VOCs inside.
A UC Davis researcher who sampled air after the Eaton fire made the same point. People assume outdoor air is the problem, particularly in Los Angeles. But indoor air is often worse, because it’s an enclosed space with its own emission sources — and after a wildfire, indoor VOC levels can run much higher than people expect.
So the question isn’t only whether your house burned. It’s whether smoke got inside, and whether what it left behind is still there.
How far does wildfire smoke actually travel?
Far enough that proximity is a poor guide.
Soot and smoke particles from a large wildfire can carry for miles — tens of miles, and in some cases over a hundred, depending on wind and terrain. A house that was never threatened by flames can still take in significant smoke through windows, doors, attic vents and HVAC intakes.
That’s why “my neighborhood was fine” isn’t the same as “my house is fine.” The fire’s footprint and the smoke’s footprint are different shapes entirely.
What does smoke leave behind inside a home?
Four categories, and they behave differently.
VOCs. Volatile organic compounds released as burned materials off-gas. This is the category the LA research found at elevated indoor levels weeks after the fires. VOCs aren’t visible and often aren’t smelled at the levels that matter.
Soot, char and ash. Fine particulate that settles on surfaces, collects in carpet and upholstery, and gets pulled into ductwork. Some of it you can see. Much of it you can’t.
Metals. Wildfires that burn structures rather than just vegetation release material from building components, wiring, and household contents.
PM2.5. Fine particulate small enough to reach deep into the lungs.
The physical residue is comparatively easy to remove. The chemical residue is the problem — it can persist in a home for months, and in some cases longer.
When should you test rather than just clean?
Cleaning first and testing afterward is a reasonable instinct, but it costs you something important: a baseline.
Test if any of these apply:
- You can smell smoke indoors, even faintly, and it returns after airing out
- There’s visible soot on windowsills, blinds, or inside light fixtures
- Your HVAC ran during or shortly after the fire
- Someone in the household has asthma, COPD, or another respiratory condition
- You’re filing an insurance claim
- You’re buying, selling, or renting out the property
- A restoration company has cleaned and told you it’s done
That last one deserves emphasis. If the company that cleaned your home is also the company telling you the cleaning worked, you don’t have verification — you have a self-assessment.
Testing and your insurance claim
This is the part homeowners most often miss, and it’s usually worth more than the test costs.
Documented testing gives your adjuster evidence rather than description. “The house smells smoky” is an opinion. A lab report showing elevated VOC or particulate levels against a control is data.
It works best in two stages. A pre-cleaning test establishes what’s actually there and supports the scope of work. A post-cleaning test demonstrates the work succeeded — or that it didn’t, which is equally useful if you’re being asked to accept a property back.
Without the first measurement, you have nothing to compare the second one to. That’s the case for testing before the restoration crew arrives, not after.
Why independence matters more after a fire than almost anywhere else
Fire restoration is a large contract. The company scoping that work has a direct financial interest in how extensive the contamination appears — and in whether the finished job passes.
We test only. A-1 performs no remediation and no restoration, which means our report isn’t a sales document for work we’d like to sell you. I have an obvious commercial interest in making that argument, and I’d rather say so plainly than pretend otherwise. But the structural point holds regardless of who makes it: the party being paid to fix the problem shouldn’t be the party certifying it’s fixed. That’s the same principle behind independent mold clearance testing after remediation.
What to do before you test
If you’re returning to a home that took on smoke, a few steps help and cost nothing:
- Ventilate. Open windows regularly to accelerate off-gassing.
- Run HVAC with a MERV 13 or higher filter. Replace the filter first — the old one is loaded with whatever it caught during the fire.
- Use HEPA air purifiers where you can.
These are the measures researchers recommended after the LA fires to reduce indoor exposure. They help. They don’t tell you whether the problem is resolved, which is what testing is for.
Don’t forget water damage
Firefighting uses enormous volumes of water, and that water goes into walls, floors and cavities.
Mold can begin growing in 24 to 48 hours in wet building materials. A property that survived the fire structurally can develop a mold problem in the weeks afterward — one that has nothing to do with smoke and won’t show up in a VOC test. If your home took water during suppression, or if a neighboring structure did, that’s a separate issue worth mold testing for.
What testing involves
A typical post-fire assessment includes a walkthrough to identify affected areas, air sampling for VOCs and particulates, surface sampling for soot and char, an outdoor control taken the same day, accredited lab analysis, and a written report you can hand to an adjuster.
The outdoor control matters as much here as it does in indoor air quality testing generally. Without it, indoor numbers have nothing to be measured against.
The bottom line
If your house burned, you already know you need help. The harder situation is the house that looks completely fine — where the family moves back in, the smell fades, and nobody thinks about it again.
The LA fire research suggests that’s exactly the scenario where exposure quietly continues. If smoke got into your home, testing tells you whether it’s still there. If it isn’t, that’s worth knowing too.
A-1 Certified Environmental Services provides independent air quality testing across Los Angeles, San Francisco, Sacramento and throughout California. Call 888-217-2719 (Los Angeles: 213-863-4011).
General information, not medical or legal advice. For health concerns following smoke exposure, consult a physician. For insurance disputes, consult your carrier or an attorney.
Carl Gibbons has over twenty years in construction and environmental science, with certifications from Pro-Lab, ESA, and MASLabs. A-1 Certified Environmental Services performs testing and inspection only, and no remediation or restoration work.