📊 AQHI runs 1 to 10+ — the higher the number, the higher the risk

The Air Quality Health Index, published by Environment and Climate Change Canada, is a scale designed to communicate short-term air-quality risk. It...

The Air Quality Health Index, published by Environment and Climate Change Canada, is a scale designed to communicate short-term air-quality risk. It runs from 1 to 10, with anything above 10 reported as 10+. Readings of 1–3 are Low risk; 4–6 are Moderate risk; 7–10 are High risk; and 10+ is Very High risk. The number is calculated from a combination of fine particulate matter (PM2.5), ground-level ozone and nitrogen dioxide. During wildfire smoke events, PM2.5 dominates and can push the AQHI well above 10. Each band carries different recommendations for the general population and for at-risk groups (children, seniors, pregnant people, anyone with heart or lung conditions). At Low risk, no precautions are needed. At Moderate, at-risk groups should consider reducing strenuous outdoor activity. At High, at-risk groups should reduce or reschedule, and the general population should consider doing the same. At Very High, everyone should reduce or reschedule strenuous outdoor activity. Check the AQHI for your community at canada.ca or through your provincial weather service before planning any outdoor exertion in smoke season. In the US, check the Air Quality Index (AQI) on AirNow (airnow.gov) instead — it is a different scale, running 0 to 500, where higher always means worse air and more reason to limit outdoor activity.

Source: Canada — About the Air Quality Health Index

Last reviewed 2026-05-02.

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