How to protect yourself from wildfire smoke indoors
Smoke affects areas hundreds of miles from the fire and lasts for weeks. How to build a clean air room and which filters actually work.
Wildfire smoke travels much farther than fire and lasts much longer. It can degrade the air of entire cities hundreds of miles away and hang around for weeks. For most people, smoke — not flame — is the part of a wildfire they will actually experience.
Why smoke is a different problem from fire
What causes harm is fine particulate matter: small enough to pass the upper airways, reach deep into the lungs and from there the bloodstream. That is why the effects are not only respiratory but cardiovascular.
A cloth mask filters droplets, not particles this size. Reducing exposure needs a particulate respirator, and it only works if it seals well against the face.
How to set up a clean air room
- Pick a room with few windows where you can spend several hours, ideally a bedroom.
- Close and seal. Windows, doors and any gap, with weather stripping tape or rolled towels.
- Filter continuously with a HEPA purifier sized for that square footage.
- Do not bring outside air in. No window fans, no exhaust fans.
- Do not add particles inside: no candles, no frying, no vacuuming without a filter, no smoking.
What to do with the HVAC system
| Equipment | What to do |
|---|---|
| Air conditioning with recirculate | Use it with the outside intake closed |
| System that only pulls outside air | Turn it off |
| Window fan or exhaust fan | Do not use while there is smoke |
| System filter | Replace with a higher-efficiency one if the unit allows it |
Signs that exposure is affecting you
Persistent cough, shortness of breath, chest tightness, headache, dizziness or palpitations. In anyone with asthma or heart or lung disease, any of these is a reason to seek medical care rather than wait and see.
- Wildfire evacuation: what to take if you have 15 minutes Wildfires move faster than any other disaster. What has to be ready beforehand and the order everything else gets picked up in.
- Defensible space: preparing the area around your home Most homes lost to wildfire are not reached by the flame front but by embers. What to do in the first five feet, and out to a hundred.
Gear that covers this
Products that match what the guide above recommends.
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HEPA air purifier
It is what captures the fine particles in smoke. Size it to the square footage of the room you intend to keep clean.
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Particulate respirator
For unavoidable trips outside. It has to seal against the face: with a beard or a poor fit it loses much of its effectiveness.
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Weather stripping tape
Smoke gets in through door and window gaps. Sealing them is the difference between filtering the air and filtering it while more comes in.
Frequently asked questions
Does a cloth mask help against wildfire smoke?
No. The fine particles in smoke are far smaller than what a cloth or surgical mask retains. You need a particulate respirator that seals against the face.
Can I run the air conditioning when there is smoke outside?
Yes, if it can run on recirculate with the fresh-air intake closed. If the system only pulls air from outside, it is better turned off.
What is a clean air room?
A room with doors and windows closed where the air is filtered continuously with a purifier, to maintain a space with fewer particles than the rest of the house.
Who is most at risk from smoke?
People with asthma or lung or heart disease, pregnant people, young children and older adults. Effects appear at lower concentrations and sooner in these groups.