What is the Air Quality Index?

The Air Quality Index (AQI) is an indicator of air quality, based on hourly pollutant measurements of some or all of the six most common air pollutants: sulphur dioxide (SO2), ground-level ozone (O3), nitrogen dioxide (NO2), total reduced sulphur (TRS), carbon monoxide (CO) and fine particulate matter (PM2.5).

With currently more than 20 sites operating, the Atlantic Region Ozone Monitoring Network is a provincial/federal partnership between Environment Canada and their partners.

• At the end of each hour, the concentration of each pollutant that the AQI station monitors is converted into a number ranging from zero upwards, using a common scale, or index. The pollutant with the highest number at a given hour becomes the AQI reading. As the air quality changes, the AQI reading increases or decreases. The lower the AQI reading, the cleaner the air.

• If the air quality value is 25 or less, the air quality is considered relatively good.
• If the AQI value is in the range of 26 to 50 (fair category), there may be some adverse effects on very sensitive people.
• An index value in the 51 to 100 range (poor category), may have some short-term adverse effects on the human or animal populations, or may cause significant damage to vegetation and property.
• An AQI value of more than 100 (very poor category) may cause adverse effects on a large proportion of those exposed.

Forecasts of the new Air Quality Health Index are available for selected locations across Canada. More locations will be added soon. More information is available at: http://www.ec.gc.ca/cas-aqhi/default.asp?Lang=En&n=065BE995-1.