How to Protect Your Home from Wildfire Smoke and PM2.5

Why Is Wildfire Smoke a Health Concern?

Wildfire smoke is more than an unpleasant smell. It contains a harmful mix of gases, hazardous air pollutants, water vapor, and particle pollution. According to the EPA, particle pollution is the main component of wildfire smoke and the principal public health threat. Learn more from the EPA about why wildfire smoke is a health concern.

The particles in smoke, often called particulate matter or PM, are a mix of solid and liquid droplets suspended in the air. Fine particles, including PM2.5, are especially concerning because they are small enough to travel deep into the lungs. Many smoke particles can also carry toxic substances, including chemicals, heavy metals, and other combustion byproducts.

Smoke exposure can cause coughing, sneezing, irritated eyes, sore throats, headaches, and shortness of breath. People with asthma, chronic obstructive pulmonary disease, lung disease, heart disease, or other respiratory conditions are especially sensitive, but poor air quality can affect everyone.

Children, older adults, pregnant people, outdoor workers, and people with heart or lung conditions may be at higher risk during wildfire smoke events. If anyone in the home has symptoms that are severe, persistent, or worsening, follow local public health guidance and seek medical advice when needed.

Because outdoor smoke can enter through windows, doors, gaps, mechanical systems, and normal air leaks, protecting your indoor air quality during wildfires is essential.

1. Stay Inside When Outdoor Air Quality Is Poor

When wildfire smoke affects your area, the safest first step is usually to stay indoors and reduce exposure to outdoor air. Keep windows and exterior doors closed, and avoid unnecessary outdoor activity until air quality improves.

The EPA’s Air Quality Index can help you understand current outdoor conditions and decide when to limit time outside. If outdoor air quality is unhealthy, focus on keeping smoke out and cleaning the air already inside your home.

During smoke events, avoid adding more pollutants indoors. Limit or avoid activities such as burning candles or incense, smoking indoors, frying or searing food, using aerosol products, and vacuuming without a HEPA-filtered vacuum.

2. Know What Is in Your Indoor Air

An indoor air quality monitor can help you understand when pollutants are rising inside your home. This is especially useful during wildfire season because smoke particles may enter even when windows and doors are closed.

Many indoor air quality monitors can measure fine particles (PM2.5), along with other indoor air quality indicators such as carbon dioxide, humidity, temperature, and volatile organic compounds (VOCs). Tracking these conditions can help you understand how wildfire smoke is affecting your home and whether your filtration and ventilation strategies are working.

Monitoring is helpful because wildfire smoke is not always obvious indoors. You may smell smoke, but elevated particle levels can occur before the air looks hazy or feels uncomfortable. Watching indoor air quality trends can also help you determine when conditions have improved enough to safely resume normal ventilation practices.

3. Stop Smoke from Coming into Your Home

During a wildfire smoke event, close windows and doors and limit activities that bring outdoor air inside. If your home has central air conditioning, use the system in recirculation mode when possible and make sure the filter is installed correctly.

You should also reduce obvious air leaks. Common problem areas include gaps around doors, windows, attic hatches, utility penetrations, and other openings in the building envelope. If smoke is entering under a door, placing a rolled-up damp towel at the bottom can help reduce short-term infiltration.

These steps do not make a home airtight, but they can reduce the amount of smoke entering your living space during the worst outdoor conditions.

4. Create a Cleaner Air Room

During heavy smoke events, it can help to create one cleaner air room where household members spend the most time. Choose a room with few windows and doors, close it off from the rest of the home, and run a properly sized portable air purifier continuously when possible.

A cleaner air room is especially useful for people who are more sensitive to smoke, including children, older adults, pregnant people, and people with asthma, heart disease, or lung conditions. Keep the room as clean as possible by avoiding candles, incense, smoking, aerosol products, and other indoor pollution sources.

If you have pets, consider whether they should stay in the cleaner air room as well. Pets can also be affected by smoke, and opening doors frequently can allow more smoky air to enter the room.

5. Use Ventilation Carefully During Smoke Events

Under normal conditions, ventilation helps remove stale indoor air, moisture, odors, and pollutants. During a wildfire smoke event, however, bringing in outdoor air may make indoor air quality worse unless that air is properly filtered.

Run your bathroom exhaust fans and range hood when showering or cooking, because moisture, combustion byproducts, grease particles, and odors can add to indoor pollution. Use them as needed, but avoid excessive exhaust operation if it pulls smoky outdoor air into the home through leaks.

If your home uses a fresh air system or air exchanger, check the manufacturer’s guidance for wildfire smoke conditions. A fresh air system can bring filtered outdoor air into the home and exhaust stale air, but during heavy smoke, filtration, recirculation settings, and proper operation become especially important.

Some fresh air systems may include upgraded filtration or recirculation modes that can help clean indoor air without constantly introducing outdoor smoke. For a broader look at ventilation and indoor air quality, read Air Purification vs Ventilation: What’s the Difference?.

6. Filter the Air Inside Your Home

Air filtration is one of the most important ways to reduce smoke particles indoors. A quality air purifier with a True HEPA filter can capture 99.97% of airborne particles as small as 0.3 microns.

A quality air purifier can help clean the air in rooms where your family spends the most time. High-quality purifiers, can also sense pollutants and automatically increase fan speed when air quality worsens, then return to a lower setting when the air improves.

When choosing an air purifier for wildfire smoke, look for a unit that is properly sized for the room. Clean Air Delivery Rate, or CADR, can help compare how quickly an air purifier can clean a room. A higher CADR generally means faster particle removal, but the right size depends on the room area, ceiling height, and how often you want the air cleaned.

If your home has a forced-air HVAC system, use the highest-efficiency filter your system can safely handle. Many wildfire smoke guidance resources recommend considering MERV 13 or higher when compatible, but homeowners should check the HVAC equipment manual or consult an HVAC professional before installing a more restrictive filter.

If you do not have an air purifier, a temporary box fan filter setup may help in an emergency when assembled and used safely. Use a high-quality HVAC filter, follow safety guidance, use a newer fan when possible, keep cords and airflow unobstructed, replace filters when dirty, and never leave a DIY filtration device unattended.

Be cautious with air cleaners that intentionally produce ozone. The California Air Resources Board warns that ozone-generating air purifiers can create a separate health hazard.

Protection Step	Why It Helps	What to Check
Close windows and doors	Reduces smoke entry from outdoors.	Check gaps, weatherstripping, and high-leakage areas.
Use recirculation mode	Limits intake of smoky outdoor air through HVAC operation.	Confirm settings on your thermostat, HVAC system, or vehicle-like controls if available.
Run a HEPA air purifier	Helps reduce fine smoke particles indoors.	Choose a unit sized for the room and replace filters as directed.
Upgrade HVAC filtration when compatible	Can improve particle capture through central air circulation.	Confirm filter size, MERV rating, airflow, and equipment compatibility.
Use ventilation carefully	Removes moisture and indoor pollutants without over-pulling smoky air.	Use exhaust fans as needed, but avoid unnecessary extended operation.

Frequently Asked Questions

Should I open windows during wildfire smoke?

No. When outdoor air quality is poor because of wildfire smoke, keep windows and exterior doors closed as much as possible. Open them only when outdoor air quality improves and local guidance says it is safe.

Can wildfire smoke get inside a closed house?

Yes. Smoke can enter through gaps, cracks, leaky doors and windows, attic openings, and mechanical systems. Closing the home helps, but filtration and air sealing are also important.

What is PM2.5 in wildfire smoke?

PM2.5 refers to fine particles that are 2.5 microns or smaller. These particles are a major concern during wildfire smoke events because they can travel deep into the lungs and contribute to respiratory and cardiovascular symptoms.

Should I run my bathroom fan during wildfire smoke?

Use bathroom fans when needed to remove moisture and odors, especially after showers. Avoid running exhaust fans longer than necessary if doing so pulls smoky outdoor air into the home through leaks.

Should I use my range hood when cooking during wildfire smoke?

Yes. Cooking adds particles, moisture, odors, and gases to indoor air. Use your range hood while cooking, especially during smoke events when indoor air is already under stress.

Is an air purifier helpful for wildfire smoke?

Yes. A properly sized air purifier with a True HEPA filter can reduce fine smoke particles indoors. Place it in the rooms where people spend the most time, such as bedrooms or living areas.

What is a clean room for wildfire smoke?

A clean room is one room in the home set up to reduce smoke exposure. It should have windows and doors closed, minimal indoor pollution sources, and a properly sized air purifier running when possible.

Should I use a MERV 13 filter during wildfire smoke?

A MERV 13 or higher filter can help capture fine particles when it is compatible with the HVAC system. Always confirm that the filter will not restrict airflow beyond what the system can safely handle.

Can whole-home ventilation help during wildfire season?

Whole-home ventilation can help under normal conditions by exchanging stale indoor air with filtered outdoor air. During heavy smoke, systems should be operated carefully according to manufacturer guidance, with attention to filtration and recirculation settings.

Are ozone air purifiers safe for wildfire smoke?

No. Avoid air cleaners that intentionally produce ozone. Ozone can irritate the lungs and create an additional indoor air quality problem.