Air Quality Index (AQI)

In Alberta, we are fortunate to be able to breathe clean air most of the time, even in our cities. However, automobile exhaust, industrial emissions and fuel combustion for heating homes and businesses, or events such as forest fires can occasionally compromise air quality.

Air quality in Alberta cities is Good over 90% of the time, according to the Air Quality Index (AQI). The index will occasionally reach into the Fair range (less than 10% of the time). Poor and Very Poor air quality conditions are rare in Alberta. The AQI is calculated and reported to the public from 22 stations in the province.

Weather conditions can contribute to adverse air quality conditions. During the winter and fall occurrence of a combination of deep temperature inversions and light winds will often create a layer of cold, stagnant air near the ground. Also, vehicles tend to idle longer and fuel consumption for heating buildings increases during cold spells. Combustion products emitted are trapped in this layer of cold, stagnant air. In Edmonton these conditions usually occur with the approach of a warm front. In Calgary, strong temperature inversions are common before the arrival of a Chinook.

Forest fire events in Alberta or neighbouring provinces can cause episodes of Poor and Very Poor air quality due to smoke being transported into urban centers. This impacts the AQI with elevated levels of particulate matter less than 2.5 micrometres (PM_2.5).

In the summer, under hot, calm weather conditions, photochemical smog can be formed through a complicated set of chemical reactions involving oxides of nitrogen and volatile hydrocarbons in the presence of sunlight. Photochemical smog has a noticeable light brown colour, and can reduce visibility and trigger a respiratory response. Ground-level ozone is a component of major concern in photochemical smog.

At Calgary in 2006, the parameters responsible for AQI values greater than 25 were ozone or PM_2.5. Of the total time in Calgary in 2006 the AQI was greater than 25, PM_2.5 was the pollutant responsible for 35% of the time, and ozone was the pollutant responsible for 65% of the time.

Likewise in Edmonton in 2006, the parameters responsible for AQI values greater than 25 were ozone or PM_2.5. Of the total time in Edmonton in 2006 the AQI was greater than 25, PM_2.5 was the pollutant responsible for 28% of the time, and ozone was the pollutant responsible for 72% of the time.

Exceedances of the one-hour Objective for ozone (0.082 ppm) generally occur infrequently in Alberta. In the year 2006 three monitoring locations in Calgary stations experienced no exceedances of the one-hour Objective and Edmonton experienced a total of 1 hour of exceedances of the one-hour Objective for all three monitoring locations.

From the statistical equivalent of the Canada-wide Standards, Alberta has adopted an Alberta Ambient Air Quality Objective for fine particulate matter (PM_2.5) of 80 µg m³ as a 1-hour average concentration.

	Air Quality Index (AQI) In Alberta, we are fortunate to be able to breathe clean air most of the time, even in our cities. However, automobile exhaust, industrial emissions and fuel combustion for heating homes and businesses, or events such as forest fires can occasionally compromise air quality. Air quality in Alberta cities is Good over 90% of the time, according to the Air Quality Index (AQI). The index will occasionally reach into the Fair range (less than 10% of the time). Poor and Very Poor air quality conditions are rare in Alberta. The AQI is calculated and reported to the public from 22 stations in the province. Weather conditions can contribute to adverse air quality conditions. During the winter and fall occurrence of a combination of deep temperature inversions and light winds will often create a layer of cold, stagnant air near the ground. Also, vehicles tend to idle longer and fuel consumption for heating buildings increases during cold spells. Combustion products emitted are trapped in this layer of cold, stagnant air. In Edmonton these conditions usually occur with the approach of a warm front. In Calgary, strong temperature inversions are common before the arrival of a Chinook. Forest fire events in Alberta or neighbouring provinces can cause episodes of Poor and Very Poor air quality due to smoke being transported into urban centers. This impacts the AQI with elevated levels of particulate matter less than 2.5 micrometres (PM_2.5). In the summer, under hot, calm weather conditions, photochemical smog can be formed through a complicated set of chemical reactions involving oxides of nitrogen and volatile hydrocarbons in the presence of sunlight. Photochemical smog has a noticeable light brown colour, and can reduce visibility and trigger a respiratory response. Ground-level ozone is a component of major concern in photochemical smog. At Calgary in 2006, the parameters responsible for AQI values greater than 25 were ozone or PM_2.5. Of the total time in Calgary in 2006 the AQI was greater than 25, PM_2.5 was the pollutant responsible for 35% of the time, and ozone was the pollutant responsible for 65% of the time. Likewise in Edmonton in 2006, the parameters responsible for AQI values greater than 25 were ozone or PM_2.5. Of the total time in Edmonton in 2006 the AQI was greater than 25, PM_2.5 was the pollutant responsible for 28% of the time, and ozone was the pollutant responsible for 72% of the time. Exceedances of the one-hour Objective for ozone (0.082 ppm) generally occur infrequently in Alberta. In the year 2006 three monitoring locations in Calgary stations experienced no exceedances of the one-hour Objective and Edmonton experienced a total of 1 hour of exceedances of the one-hour Objective for all three monitoring locations. From the statistical equivalent of the Canada-wide Standards, Alberta has adopted an Alberta Ambient Air Quality Objective for fine particulate matter (PM_2.5) of 80 µg m³ as a 1-hour average concentration.