What is an Air Quality Index?

The Air Quality Index (AQI) represents how clean the air is. The lower the index is, the better the quality of the air.

The AQI provides a number which is easy to compare between different pollutants, locations, and time periods.

What does this mean for me?

Each category in the AQI corresponds to a different level of health risk:

Description Air Quality Index Description of Potential Health Risks
Very Good
0-33 Air quality is considered good, and air pollution poses little or no risk.
34-66 Air quality is considered good, and air pollution poses little or no risk.
66-100 Air quality is acceptable. However, there may be a health concern for very sensitive people.
100-150 The air quality is unhealthy for sensitive groups, such as people with lung disease or heart disease. The general population is not likely to be affected.
Very Poor
150-200 Everyone may begin to experience health effects, especially those from sensitive groups.
200+ Everyone may experience health effects. In Canberra, the AQI only reaches this level during major bushfires or dust storms.

How the Air Quality Index is calculated?

ACT Health collects the data from remote monitoring stations in various scientific units, such as parts per million (ppm) and micrograms per cubic meter (µg/m3). As the units, time frames and exposure standards are different for different pollutants this can make it hard to compare numbers in a meaningful way. Where the standards are reported as more than an hourly average, a rolling average is calculated.

An Air Quality Index is calculated based on the relevant Air NEPM standard, or advisory standard, for that pollutant as follows:


Air Quality Index (AQI) is equal to pollutant concentration over pollutant standard multiplied by 100

This means that at an index value of 100 the pollutant is currently at a concentration equal to an environmental standard level.

Both the data reading and the derived AQI are published on the ACT Health website. A site AQI is taken to be the highest AQI of any pollutant. A daily AQI is the highest site AQI recorded in that 24 hour period.