Skip outdoor exercise when AQHI is high
People doing strenuous outdoor activity are among those most at risk from wildfire smoke because exercise increases breathing rate and depth, drawing...
People doing strenuous outdoor activity are among those most at risk from wildfire smoke because exercise increases breathing rate and depth, drawing more PM2.5 into the lungs. Health Canada recommends reducing or rescheduling outdoor activity during smoke events, scaled to the AQHI level. At AQHI 4–6, at-risk groups should consider reducing strenuous activity. At 7–10, the general population should reduce or reschedule, and at-risk groups should avoid strenuous outdoor activity entirely. At 10+, everyone should avoid strenuous outdoor activity. In the US, follow the same logic using the AirNow AQI (airnow.gov) — the higher the number on its 0–500 scale, the more reason to move exercise indoors. Move workouts indoors when smoke is bad — community centres and gyms with HVAC filtration are good options. Levels indoors are usually lower than outside, but not zero, so check your facility’s air handling. If you must exercise outside, choose lower-intensity activities, exercise during the part of the day when AQHI is lowest (often early morning), and stop if you experience headache, chest tightness, dizziness or unusual shortness of breath. An N95 respirator filters particles but makes breathing harder and is not designed for sustained vigorous exercise.
Vigorous outdoor exercise during heavy smoke can pull PM2.5 deep into the lungs at five-to-ten times the resting rate — which is why Health Canada says to reschedule, not push through.
Source: Canada — Protecting Your Physical and Mental Health
Last reviewed 2026-05-02.
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