Wildfire Indoor Air Quality: How to Protect Your Home from Smoke

Wildfire smoke poses a major risk to indoor air quality, even in homes far from active fires. As organic materials burn, they release fine particles, volatile organic compounds, and gases that can drift for miles. These airborne particles can enter indoor spaces and may worsen symptoms in people with chronic heart or lung conditions, especially in older adults, children, and people with asthma or other respiratory conditions.

Breathing smoke indoors may cause discomfort, such as eye, throat, or lung irritation, and could worsen symptoms in people with respiratory issues. This article outlines practical steps to improve wildfire indoor air quality, including using portable air cleaners, HVAC filters, and safe cleanup methods during smoke events.

Wildfire smoke can easily find its way indoors, especially in older homes or buildings with poor sealing. During smoke events, it’s essential to understand how outdoor air enters to take steps that protect your indoor air quality.

Even if your windows are closed, smoke can still seep into your home through unnoticed openings. A well-sealed home helps block harmful airborne particles and improves indoor air during wildfire smoke events.

Common smoke entry points include:

• Cracks or gaps around windows, doors, or foundations

• Bathroom and kitchen vents without proper seals

• HVAC systems or fresh air intake ducts pulling in outdoor air

• Gaps around plumbing or cable lines that enter through walls

Staying informed about outdoor air quality is key during wildfire season. Resources like the Air Quality Index (AQI) can be used to track PM2.5 levels, the fine particles produced when organic materials burn.

The California Air Resources Board and other agencies may issue public advisories such as “Spare the Air” alerts in wildfire-prone regions. These warnings help residents know when to stay indoors, avoid breathing smoke, and prepare indoor spaces to prevent wildfire smoke indoors.

Keeping smoke out starts with sealing the areas where it can get in. Even minor improvements can reduce exposure to particulate matter and protect your home’s air quality during wildfire smoke events.

Gaps around windows and doors are easy ways for smoke to enter. Inspect these areas closely and use weatherstripping to seal door frames. Apply caulk around window sills, wall cracks, or utility line entries. Sealing these small gaps can reduce the amount of fine particles entering the home and help maintain cleaner indoor air.

Installing a door sweep or draft stopper at the bottom of exterior doors can make a noticeable difference. These tools block smoke and other microscopic particles from sneaking under the door. They're affordable, simple to use, and effective for reducing wildfire indoor air quality issues.

If your windows don’t seal tightly, use temporary plastic seals, or specialized window covers to block out smoke. Cover or close off vents not in use—especially kitchen or bathroom vents—unless they're essential for combustion appliances. Keep safety in mind and ensure proper ventilation, but limiting unnecessary outdoor air access is critical during heavy smoke conditions.

Ventilation during wildfire smoke events requires careful planning. Bringing in outdoor air during poor air quality conditions can introduce harmful airborne particles into your home.

Keep windows and doors shut when the Air Quality Index (AQI) shows hazardous levels, especially during active smoke events. In some cases, early mornings or periods of lower smoke levels may allow for a brief airing out to reduce indoor CO₂ buildup. Always check local AQI updates in real-time before ventilating, and limit this to short periods when outdoor air shows improvement.

Exhaust fans and HVAC systems can either help or hurt indoor air quality, depending on their use.

Tips to manage HVAC and exhaust systems:

• Run kitchen and bathroom exhaust fans only when needed, as they can pull wildfire smoke indoors if the home has negative air pressure.

• Set your  HVAC system to recirculate mode  to prevent it from pulling in smoky outdoor air through the fresh air intake.

• Use a MERV 13+ HVAC filter or higher-rated HVAC filter, and consider portable HEPA air purifiers for added protection in individual rooms to help remove smoke particles from circulating air.

• Pair the system with a portable air cleaner to improve filtration in commonly used rooms.

Portable fans help circulate clean air inside, but placement is key. Keep them away from open windows unless outdoor AQI has significantly improved. Use fans to move air through filtered zones rather than pull in outside air. The goal is to steady airflow indoors without introducing new fine particles.

Filtering out particulate matter and volatile organic compounds during a wildfire is essential. With the right tools, you can significantly reduce exposure to microscopic particles in indoor spaces.

A HEPA filter can trap PM2.5 particles commonly found in wildfire smoke. To handle gases and odors, consider activated carbon filters. For your HVAC system, check the MERV rating of the filter—MERV 13 or higher is best during smoke events to capture more harmful particles and protect the respiratory system.

A portable air cleaner works well for individual rooms, especially if your HVAC system can't support a higher-rated filter. Place purifiers in bedrooms or living rooms for best results. Clean or replace filters often, especially during prolonged exposure to smoke, to maintain their effectiveness.

In a pinch, taping a MERV-rated HVAC filter to the front of a box fan is a simple way to improve wildfire indoor air quality. Though not as powerful as commercial filters, it can help reduce smoke levels in small rooms. Ensure the fan motor stays cool, and avoid placing the unit near flammable materials during use.

Keeping your indoor space clean and smoke-free goes beyond air filters. Everyday actions can protect or worsen indoor air conditions during wildfire smoke events.

Cooking—especially frying or broiling—produces fine particles that can worsen indoor air quality. If possible, cook less or use lower-temperature methods. Avoid harsh chemical cleaners that release fumes, especially with windows sealed. Use a range hood vented outdoors if you must cook, and clean hard surfaces gently to avoid stirring up dust or ash.

Skip candles, incense, and wood-burning stoves during smoke events. These release more particles and volatile organic compounds, adding to the complex mixture already inside. Avoid smoking indoors, as it can increase indoor pollution and may cause symptoms like runny nose or eye irritation.

Open doors as little as possible during heavy smoke periods. Run errands or take out trash when the AQI improves. If you need to go in and out, do it quickly to prevent smoke from rushing inside and compromising the clean air you’ve worked to maintain.

Getting ahead of wildfire smoke means preparing your home before the season begins. Simple upgrades and smart planning can protect indoor air quality and reduce exposure to harmful airborne particles.

Making a few upgrades to your home can significantly reduce the risk of wildfire smoke indoors and help maintain cleaner indoor air during fire season.

Consider the following improvements:

• Install high-quality double or triple-pane windows with tight seals to block smoke.

• Add mechanical ventilation systems with HEPA filters or advanced filtration options.

• Upgrade to an HVAC system that supports MERV 13–16 filters, if compatible with your system, to improve filtration efficiency.

While focused on outdoor safety, smart landscaping can also protect your home from smoke exposure. Keep bushes and trees trimmed back from your home to reduce flammable material close to the structure. Clean gutters and vents regularly so embers can’t enter. These changes reduce the risk of fire damage and lessen smoke levels around your home.

Prepare a wildfire safety kit well in advance. Keep N95 or P100 masks for safe breathing if you must go outside. Include any necessary medications, water, flashlights, and copies of important documents. Being ready helps reduce stress and ensures fast decisions during smoke events or sudden evacuations.

Keeping smoke out of your home is possible with the right actions. Sealing leaks, using HEPA filters, setting HVAC systems to recirculate, and managing indoor sources of pollution can significantly improve wildfire indoor air quality. Preparing your home for wildfire season—through upgrades, filtration systems, and emergency planning—helps protect your health and comfort all year.