How Wildfire Smoke Affects Indoor Air Quality
Learn how wildfire-smoke PM2.5 can enter buildings, why indoor air is not automatically smoke-free, and how filtration and ventilation choices affect exposure.
Buildings reduce exposure, but they are not airtight
Outdoor smoke can enter through open doors and windows, leaks in the building envelope, and mechanical ventilation. Indoor particle levels are often lower than outdoors in a well-managed building, but they can still become elevated during a prolonged smoke event.
PM2.5 is the main health concern in wildfire smoke
Fine particulate matter can travel deep into the lungs and is the main wildfire-smoke health risk highlighted by Health Canada. Because these particles are tiny, you cannot judge indoor air quality only by whether you can see haze or smell smoke.
Filtration and source control work together
Reducing infiltration, using suitable HVAC filtration, running properly sized portable air cleaners, and avoiding unnecessary indoor particle sources can help. Filters need maintenance because clogged filters become less effective and can impair airflow.
Heat changes the decision
Closing a home tightly during extreme heat can create a different health hazard. Federal guidance emphasizes staying cool as well as reducing smoke exposure. If your home cannot remain both cool and reasonably clean, seek a local cleaner-air or cooling space when available.
Common questions
Why do I smell smoke with the windows closed?
Buildings have air leakage and ventilation pathways, so outdoor smoke can still enter. Odour also does not provide a precise measurement of particle concentration.
Can a portable air cleaner remove all wildfire smoke?
A suitable air cleaner can reduce fine particles in the room it is sized for, but it does not make a building perfectly smoke-free or remove every gas in smoke.
Should I use AQHI to measure my indoor air?
AQHI is an outdoor health-risk index. It is not a direct measurement of the air inside your home.
Official and trusted sources
FireRadar summarizes these resources in plain language. Follow the source itself for the newest guidance, local instructions, eligibility rules, or operational decisions.
Federal health guidance on PM2.5, symptoms, exposure reduction, indoor air, and wildfire smoke.
Preparation guidance for respirators, filters, portable air cleaners, medications, and cleaner indoor air.
Current federal hub for wildfire smoke, AQHI, alerts, preparation, and health guidance.
Related FireRadar resources
Practical steps to reduce wildfire-smoke particles indoors using windows and doors, HVAC filtration, portable air cleaners, and a cleaner-air room.
Understand Canada's AQHI scale from 1 to 10+, what low, moderate, high, and very high risk mean, and how wildfire smoke can change air-quality health risk quickly.
Learn when a well-fitting N95 or equivalent respirator may help reduce wildfire-smoke particle exposure, what it cannot filter, and why fit matters.
Open province, territory, wildfire, hotspot, smoke, and AQHI map views from the FireRadar directory.