Wildfire Smoke Got Into Your House? Here’s How to Clear It (and When You Can’t Do It Yourself)

Oregon DEQ recorded 29 days with unhealthy air quality levels from wildfire smoke between 2013 and 2024 in the Portland metro. That is not an isolated bad year or two. It is a pattern, and the seasons are getting longer. For homeowners in the Portland and Vancouver area, wildfire smoke is now a regular annual threat, not an occasional nuisance.

This post explains what smoke does to your home, what you can do during an event to reduce indoor exposure, and when porous surfaces have absorbed enough smoke that an air purifier cannot fix it.

How Wildfire Smoke Gets Into Your Home

The most common assumption is that smoke enters through open windows and doors. That is one path, but it is not the main one during a serious smoke event when most homeowners have everything closed tight.

HVAC systems are the biggest vulnerability. Most return air is pulled from inside the home, but any system with an outdoor air exchange unit pulls fresh air directly from outside. Older HVAC systems and leaky ductwork can also draw outdoor air in through gaps at joints and penetrations. During an air quality event, a running HVAC system with any outdoor air pathway is actively pumping smoke-laden air through your ducts and into every room.

Beyond HVAC, smoke infiltrates through gaps around windows and door frames, through electrical outlets on exterior walls, and through attic access hatches that are not well-sealed. This matters more in older construction. Many homes in Portland and Vancouver were built before modern tight-envelope standards. Older homes cycle outdoor air into the interior at a much faster rate than newer, well-insulated construction, which means a smoke event outside translates to elevated indoor smoke concentrations much more quickly.

Why Indoor Smoke Is a Health Problem, Not Just an Odor Problem

The primary hazard from wildfire smoke is PM2.5, particulate matter with a diameter of 2.5 microns or smaller. These particles are small enough to bypass the nose and throat and penetrate deep into the lower airways and lungs. They carry combustion byproducts including carbon monoxide, volatile organic compounds, and heavy metals from whatever burned.

The EPA and Oregon DEQ both classify PM2.5 as a serious health hazard at elevated concentrations. The AQI scale that DEQ uses places anything above 100 in the Unhealthy for Sensitive Groups range and anything above 150 in the Unhealthy range for all populations. During the worst wildfire events in the Portland metro, AQI has exceeded 250, which falls in the Very Unhealthy category.

Children, elderly adults, and people with asthma, COPD, or cardiovascular conditions are most vulnerable to PM2.5 exposure. But elevated PM2.5 indoors is a risk for healthy adults as well, especially during prolonged events. The smell is a signal, not the problem itself. Treating smoke as an odor issue understates the actual health stakes.

DIY Steps That Actually Help During a Smoke Event

When outdoor AQI is elevated and smoke is getting in, here is what makes a real difference:

• Turn off or minimize HVAC. If your system has any outdoor air intake, running it during a smoke event pumps smoke through the ducts. If you cannot turn it off entirely, seal return vents with tape to reduce outdoor air draw until the event passes.
• Switch to MERV-13 or higher air filters. Standard 1-inch fiberglass filters capture large debris but do almost nothing for PM2.5. MERV-13 filters are rated to capture particles in the 0.3 to 1.0 micron range, which is where PM2.5 sits. Install one before a smoke event if you can anticipate it, and replace the filter immediately after the event ends because it will be heavily loaded with captured particles.
• Use a portable air purifier with a true HEPA filter. True HEPA filtration captures 99.97% of particles 0.3 microns and larger. Run it in the room where you spend the most time, particularly the bedroom overnight. Size matters: a purifier rated for 200 square feet will not meaningfully clean a 600-square-foot open-plan space.
• Do not use ozone generators. Ozone machines are marketed for odor removal and are sometimes suggested for smoke. Ozone at concentrations effective for odor control is harmful to breathe and is especially dangerous for people with respiratory conditions. Do not use them in occupied spaces.
• Minimize door and window openings. If you must ventilate, do it in the early morning hours when outdoor AQI is typically at its daily low before daytime heating drives smoke back down. Check the DEQ AQI forecast at the Oregon DEQ AQI website before opening anything.
• Wipe down hard surfaces with a damp cloth. PM2.5 settles onto horizontal surfaces throughout the home. A damp wipe picks up settled particles; a dry cloth redistributes them back into the air.

When DIY Is Not Enough: The 72-Hour Threshold

Air purifiers address airborne particles. They cannot remove smoke that has already absorbed into your home’s materials. If smoke has been present in the home for more than 72 hours, the odor is not just in the air. It is in the carpet, upholstered furniture, drywall, insulation, wood trim, and every other porous surface that has had time to absorb it.

The pattern is predictable: the event passes, you ventilate the home, the smell seems better. Then the weather shifts and the temperature changes, and the odor comes back. That happens because the source is still there. Warming temperatures cause absorbed volatile compounds to off-gas out of the material they are trapped in. Running a fan or air purifier does not remove what is already inside the structure.

HVAC duct contamination compounds the problem. Smoke deposits accumulate on duct walls, on coils, and in the air handler. Every time the system runs after a smoke event, it redistributes those deposits through the home. Smoke damage remediation for HVAC systems requires professional cleaning of the ductwork, not just a filter swap.

The indicator that you need professional help is straightforward: if the odor persists more than 72 hours after you have ventilated the home and the outdoor event has passed, the smoke is in the structure, and an air purifier will not clear it.

What Professional Smoke Remediation Involves

Fire and smoke restoration for wildfire-related indoor contamination is more involved than airing out the home, and it addresses the sources rather than the symptoms.

The process typically includes several approaches, sometimes used in combination depending on the extent of contamination:

• HEPA dry vacuuming of surfaces. Before any other treatment, settled smoke particles are removed from surfaces with HEPA-filtered vacuums that capture rather than redistribute them.
• Thermal fogging. A petroleum-based deodorizing fog penetrates porous surfaces and pairs chemically with odor molecules, neutralizing them inside the material rather than masking the surface.
• Hydroxyl generation. Hydroxyl generators produce hydroxyl radicals, the same molecules the atmosphere produces through UV-sunlight interaction, that break down volatile organic compounds at a molecular level. Unlike ozone treatment, hydroxyl generation is safe in occupied spaces.
• Ozone treatment (unoccupied structures only). At high concentrations in a sealed, unoccupied space, ozone is effective at neutralizing embedded smoke odors. The space must be vacated and thoroughly ventilated before reoccupancy. This is a professional tool, not a consumer one.
• HVAC duct cleaning. Ductwork is cleaned with high-powered negative air pressure equipment that removes smoke deposits from inside the ducts before the system is run again.
• Content cleaning. Clothing, soft furnishings, books, and other porous contents that absorbed smoke are cleaned through ozone chambers, ultrasonic cleaning, or specialized laundering depending on the material.

The right combination depends on how long smoke was present, which materials were affected, and the extent of HVAC contamination. A restoration professional will assess the home and scope the work before recommending a treatment plan.

Resources and Next Steps

For current AQI conditions during a smoke event, Oregon DEQ publishes real-time air quality data at oregonsmoke.oregon.gov and through the AirNow app, which displays the EPA AQI index for your specific location. Clark County in Washington tracks conditions through the Southwest Clean Air Agency. These are the best sources for knowing when it is safe to ventilate.

If you experienced significant smoke infiltration this season and you are noticing persistent odor, that is worth addressing before the next season. Smoke compounds that sit in insulation, carpet, and HVAC systems do not dissipate on their own over time. For more on managing the aftermath of a fire-related event, see our checklist for what to do after a house fire.

If you want to know whether your home needs professional remediation or whether your situation is manageable with the DIY steps above, call us. We will give you a straight answer about what we are seeing and what, if anything, needs to be done.