Wildfire Smoke at Home: How to Build a Cleaner-Air Room

Wildfire smoke does not have to be nearby to affect your household. Smoke can travel hundreds of miles, settle into valleys, and enter homes through windows, doors, ventilation systems, and small openings.

You may not be able to keep every particle out of your home. You can, however, concentrate your efforts on one room where household members can spend time breathing cleaner air.

A cleaner-air room is not a sealed bunker. It is simply a comfortable room where you reduce incoming smoke, filter the indoor air, and avoid activities that create additional pollution.

Preparing that room before smoke arrives makes it far more useful when outdoor air quality deteriorates.

WHAT MAKES A GOOD CLEANER-AIR ROOM?

Choose a room where your household can comfortably spend several hours. A bedroom with an attached bathroom can work well, although any room with a door and relatively few windows may be suitable.

The room should:

• Be large enough for the people and pets who may use it

• Have windows and doors that close securely

• Remain at a safe temperature

• Have enough electrical outlets for an air cleaner and essential devices

• Be away from obvious indoor pollution sources

• Have an exit that remains easy to use during an emergency

Do not select a room that becomes dangerously hot when its windows are closed. Heat can become a more immediate health threat than smoke, particularly for older adults, infants, pregnant people, and people with certain medical conditions.

CONTROL THE AIR COMING INSIDE

When smoke levels rise, close the room’s windows and doors. You can place a clean towel at the bottom of a noticeably drafty door, but do not obstruct an emergency exit.

If your heating or cooling system allows it, switch it to recirculate so it is not continuously pulling smoky outdoor air into the home. Close or reduce the outdoor-air intake when the system’s instructions allow you to do so safely.

If you use a window air conditioner, confirm that the outdoor-air damper is closed and that the unit forms a reasonably tight seal around the window.

Single-hose portable air conditioners can pull outdoor air into a room as they exhaust warm air. The EPA recommends using these units sparingly during heavy smoke unless no safer cooling option is available.

Never sacrifice safe indoor temperatures in an attempt to keep smoke outside. If the home becomes too hot, look for a cleaner-air center, cooling center, public building, or another safe location with filtered air.

FILTER THE ROOM CONTINUOUSLY

A portable air cleaner is usually the simplest way to remove smoke particles from a single room.

Choose a filter-based model with a HEPA filter. Avoid devices marketed primarily as ionizers, ozone generators, electrostatic precipitators, or ultraviolet air purifiers. Some of these products can produce ozone, which is a lung irritant.

The cleaner must be appropriately sized for the room. Washington State Department of Health recommends checking the smoke Clean Air Delivery Rate, or CADR. For heavy smoke, its sizing example pairs a 400-square-foot room with a smoke CADR of approximately 400 cubic feet per minute.

Place the cleaner where air can move freely around it:

• Keep the intake and outlet away from walls, curtains, and furniture

• Position it away from open doors and strong drafts

• Keep it out of reach of young children and pets

• Run it on the highest setting your household can comfortably tolerate

During a smoke event, operate the cleaner continuously rather than waiting until the room smells smoky. Fine particles can be present even when you cannot see or smell them.

Check the filter regularly. Replace it according to the manufacturer’s instructions or sooner if it becomes heavily soiled, produces a smoky odor, or noticeably reduces airflow.

USE YOUR CENTRAL SYSTEM WHEN APPROPRIATE

A central heating or cooling system may also help filter household air.

The EPA generally recommends a filter rated MERV 13 or higher when the system can safely accommodate it. A filter that is too restrictive for your equipment can reduce airflow or damage the system, so check the manufacturer’s instructions or ask a qualified HVAC professional before changing filter types.

During smoke events:

• Use the system’s recirculation setting when available

• Keep the fan running if the system is designed to operate that way

• Check the filter more frequently

• Replace dirty filters promptly

Central filtration can support the entire home, but a portable cleaner in one selected room gives the household a more concentrated place of refuge.

A DIY CLEANER CAN BE A TEMPORARY OPTION

If a commercial air cleaner is unavailable or unaffordable, a properly constructed do-it-yourself air cleaner can reduce airborne particles.

EPA research supports designs that use a MERV 13 filter attached securely to a newer box fan. A shroud around the front of the fan can improve performance, while thicker filters or multiple-filter designs can increase airflow.

For safer operation:

• Use a newer fan manufactured in 2012 or later

• Look for a UL or ETL safety certification

• Use a filter at least as large as the fan

• Make sure airflow follows the arrow printed on the filter

• Keep the fan away from curtains, water, and walkways

• Do not use an extension cord unless the fan manufacturer allows it

• Check the filter daily during heavy smoke

• Never leave a questionable, damaged, or overheating fan running unattended

The EPA describes DIY air cleaners as a temporary alternative, not a permanent replacement for a tested commercial unit.

STOP MAKING THE INDOOR AIR WORSE

Filtering works better when the household is not adding more particles and gases to the room.

During smoky conditions, avoid:

• Burning candles, incense, or wood

• Smoking or vaping indoors

• Using aerosol sprays, air fresheners, or diffused oils

• Frying or broiling food

• Using gas or propane appliances unnecessarily

• Sweeping or dusting in ways that send particles into the air

• Vacuuming unless the vacuum has an effective HEPA filter

Cooking can generate significant indoor pollution. During severe smoke, favor foods that require little cooking or use appliances that produce fewer particles.

BUILD THE ROOM AROUND YOUR HOUSEHOLD

A cleaner-air room should support the people and animals using it, not just contain an air cleaner.

Consider keeping the following nearby:

• Drinking water

• Regular medications

• Phone chargers and a charged power bank

• A flashlight

• Quiet activities for children

• Pet food, water, medications, and a carrier or leash

• Copies of important contact information

• An N95 respirator for each household member who can safely and properly wear one

• A battery-powered radio if internet or cellular service becomes unreliable

People with asthma, COPD, heart disease, diabetes, or other conditions should follow the smoke plan developed with their healthcare provider. Keep rescue medications and other necessary supplies accessible.

Respirators can reduce exposure while someone must be outside, but they do not replace cleaner indoor air. An N95 must fit closely to the face, and it does not filter harmful gases. People with heart or lung conditions should consult a healthcare professional if they have questions about safely using one.

WATCH THE AIR—NOT ONLY THE SKY

Do not rely on visibility or smell to judge whether outdoor air is safe. Fine smoke particles can remain elevated even when the sky appears clearer.

Use Washington’s air-quality information and the AirNow Fire and Smoke Map to monitor:

• The current Air Quality Index

• Smoke forecasts

• Nearby fires

• Temporary air monitors

• Periods when outdoor air improves

If conditions improve, briefly ventilate the home to release pollutants that accumulated indoors. Close the windows again if smoke levels begin rising.

During a long smoke event, Washington DOH recommends taking advantage of cleaner periods to bring fresh air inside, provided the outdoor air is genuinely better and the home can remain at a safe temperature.

KNOW WHEN THE HOUSE IS NOT THE SAFEST PLACE

A cleaner-air room reduces exposure, but it cannot make every home safe under every condition.

Consider relocating to a cleaner-air center, public building, or another safe indoor location if:

• The room cannot remain cool enough

• Smoke continues entering faster than it can be filtered

• The air cleaner cannot operate because of an outage

• Someone develops worsening symptoms

• A household member requires equipment that cannot operate reliably

• Local officials issue an evacuation order

Smoke exposure can cause burning eyes, coughing, headache, fatigue, wheezing, shortness of breath, chest pain, or an irregular heartbeat.

Seek medical attention for serious symptoms such as chest pain or difficulty breathing. Follow instructions from healthcare professionals and local authorities.

AFTER THE SMOKE IMPROVES

When official air-quality readings show sustained improvement:

• Open windows and doors to ventilate the home

• Continue running air cleaners for at least a few additional days

• Check portable and central-system filters

• Replace filters that are dirty or smell smoky

• Wipe surfaces with a damp cloth

• Wash bedding and other fabrics that collected smoke

• Restock any supplies used during the event

Then review what worked. Note whether the room stayed comfortable, whether the cleaner was powerful enough, and what the household wished it had available.

That short review will make the next smoke event easier to manage.

YOUR CLEANER-AIR ROOM SETUP CARD

Room selected: ______________________________

Room size: __________________ square feet

Portable cleaner smoke CADR: __________________

Replacement filter location: ______________________________

HVAC recirculation setting confirmed: Yes / Not yet

Medications and essential devices ready: Yes / Not yet

Pet supplies ready: Yes / Not applicable / Not yet

Safe alternate location: ______________________________

Local alert system: ______________________________

Preparing one room will not eliminate every risk from wildfire smoke. It gives your household a practical, maintainable place to begin—and a dependable system you can improve over time.

OFFICIAL RESOURCES

Washington State Department of Health: Protect Yourself From Wildfire Smoke
https://doh.wa.gov/community-and-environment/air-quality/smoke-fires/protect-yourself-and-others

Washington State Department of Health: Choosing a Portable Air Cleaner
https://doh.wa.gov/community-and-environment/air-quality/indoor-air/portable-air-cleaners/choosing

Washington State Department of Health: Using a Portable Air Cleaner
https://doh.wa.gov/community-and-environment/air-quality/indoor-air/portable-air-cleaners/using

Washington Department of Ecology: Wildfire Smoke
https://ecology.wa.gov/air-climate/air-quality/smoke-fire/wildfire-smoke

AirNow Fire and Smoke Map
https://fire.airnow.gov/

EPA: How to Create a Cleaner-Air Room at Home
https://www.epa.gov/wildfires/how-create-cleaner-air-room-home

EPA: Research on DIY Air Cleaners
https://www.epa.gov/air-research/research-diy-air-cleaners-reduce-wildfire-smoke-indoors

Weatherstead provides general educational information, not emergency, medical, legal, or professional safety advice. Follow current instructions from local authorities, product manufacturers, healthcare providers, and qualified professionals.