How to Lower Your Exposure to Wildfire Smoke
Short answer: Lower your smoke exposure by keeping it outside and cleaning what is inside. Close windows and doors, run a HEPA purifier sized to the room, set air conditioning to recirculate, and wear a well-fitting N95 or KN95 when you go out. Also stop adding indoor air quality problems of your own — candles, frying and smoking.
What is actually in wildfire smoke
Wildfire smoke is a mixture of gases and fine particles. The component that matters most for health is PM2.5 — particles smaller than 2.5 micrometres, roughly one thirtieth the width of a human hair. They travel deep into the lungs, cross into the bloodstream, and are linked to respiratory and cardiovascular effects within days of heavy exposure.
Smoke also carries carbon monoxide, volatile organic compounds and, depending on what burned, measurable heavy metals. This is one reason wildfire smoke is not the same as woodsmoke from a clean stove: the mix varies with fuel, temperature and distance travelled.
Step 1: keep outdoor smoke out
When the air quality index climbs, the goal is a sealed indoor space. Close windows and exterior doors, including the one you keep propped open for the dog. Set your air conditioning to recirculate rather than drawing in outside air, and close the fresh-air intake if your system has one. If you have a central system, upgrade to a MERV 13 filter if it is compatible; that alone captures a meaningful share of smoke particles.
Seal obvious gaps — a towel along a drafty door base, tape over a window that will not close properly. Also run bathroom and kitchen extractor fans less, since they pull air (and smoke) in from outside.
Step 2: clean the air inside
A portable HEPA air purifier is the single most effective indoor measure. Size it properly: the CADR rating should be roughly two thirds of the room's floor area in square feet for one air change per hour, and more if you want faster cleaning. A purifier that is too small for the room will make a measurable but insufficient difference.
Run it in the room where you spend the most time, and move it to the bedroom at night. Keep doors closed so you are cleaning a defined volume rather than the whole house.
If a HEPA unit is out of reach, a DIY box fan filter — a 20-inch fan taped to a MERV 13 furnace filter — has been shown in independent testing to reduce indoor particle levels substantially, for a fraction of the cost. Avoid ozone generators entirely; they are not effective against smoke particles and add a lung irritant of their own.
Step 3: protect your airways when you go out
Cloth masks and surgical masks do not seal well enough to filter fine particles meaningfully. A NIOSH-approved N95 or a well-fitting KN95 is the right tool. Fit matters as much as the rating: a mask that leaks around the nose or cheeks is filtering far less than its label suggests.
Reduce the time outdoors, and move exercise indoors. Hard breathing during a run pulls far more smoke deep into the lungs than walking does, which is why public-health advice during smoke events is to skip outdoor workouts rather than to just wear a mask through them.
Check your local air quality index before planning time outside, and remember that conditions can change within a day. If you can smell smoke indoors, your particle levels are already elevated.
Step 4: stop adding to the indoor load
Indoor combustion is the most controllable source of fine particles in most homes — more controllable than the wildfire itself.
| Source | What helps |
|---|---|
| Candles and incense | Skip them during smoke events; they add particles and odour |
| Frying and broiling | Use the extractor fan or cook methods that produce less smoke |
| Tobacco and vaping indoors | Take it outside or stop; indoor air quality is the first casualty |
| Fireplace or wood stove | Do not use on smoke-event days |
| Vacuuming | Use a HEPA-filtered vacuum, or damp-wipe instead |
Water and food are a separate topic, but worth a line: if you rely on tap water, a certified carbon filter reduces many contaminants, and if there is a local boil-water notice after a fire, follow it. Store food covered during heavy smoke, and choose cookware you are comfortable with — none of these replace the steps above, but they are part of the same environmental exposure picture.
Who is most at risk
Children breathe more air per kilogram of body weight and their lungs are still developing. Pregnant women, older adults, and anyone with asthma, COPD, heart disease or diabetes face higher risk. If someone in your household has asthma, make sure their reliever inhaler is at hand and that a written action plan is up to date before smoke season arrives rather than during it.
Seek medical care for chest tightness, wheezing that does not settle, difficulty breathing at rest or palpitations during a smoke event — do not wait it out.
Key takeaways
- Fine particles (PM2.5) are the main health concern in wildfire smoke and travel deep into the lungs and bloodstream.
- Closing windows, recirculating air conditioning and using a MERV 13 filter keeps a meaningful share of smoke outside.
- A correctly sized HEPA purifier, or a DIY box fan filter, is the most effective indoor measure; ozone generators are not.
- N95 or KN95 masks filter fine particles; cloth masks do not seal well enough to matter.
- Skip indoor candles, frying smoke, fireplaces and tobacco during smoke events, and move exercise indoors.
Frequently asked questions
Should I wear a mask indoors during a wildfire smoke event?
Usually not necessary if you are running a HEPA purifier and keeping windows closed. Masking indoors is reasonable when your air quality is otherwise uncontrollable — for example if you must share a smoky space.
Do air purifiers really help with smoke?
Yes, when they are HEPA units correctly sized for the room. Independent testing of DIY box fan filters also shows large reductions in indoor particles at low cost. The key variables are filtration grade, room size and keeping doors closed.
Can I exercise outside when the air is smoky?
If the air quality index is in the unhealthy range, move the workout indoors. Hard breathing increases the dose of particles reaching deep lung tissue far more than the same time spent walking.
How do I know when it is safe to open the windows again?
Watch your local air quality index and the smoke plume forecast, not just the sky. When levels return to moderate and the smell is gone, ventilate the house thoroughly before going back to your normal routine.
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