Measuring air quality

ACT Health reports on air quality using up-to-date, accurate data on levels of pollutants in the air. Air quality is also presented as an Air Quality Index (AQI) rating at each of the ACT’s three monitoring stations.

Air Quality Index

The Air Quality Index (AQI) is a scale of air pollution that gives Canberrans an indication of how clean the air is so we can change our outdoor activities if pollution levels are high.

The AQI is calculated from air quality data relating to the five pollutants that are monitored in the ACT. For each pollutant, the AQI is the data value expressed as a percentage of the level specified by the National Environment Protection Measure for Ambient Air (NEPM) standard.

AQI is not used for the purpose of providing health advice. For detailed health advice on air quality  and pollen please go to the Air Quality Health Advice Portal.

There are six AQI categories ranging from ‘Very good’ to ‘Hazardous’. Each category is shown in a different colour. 

A lower value indicates better air quality, and a higher value indicates poorer air quality. 

When a pollutant AQI is poor, very poor and hazardous, this means the pollutant has exceeded its corresponding air quality standard. 

Very Good ●
Good ●
Fair ●
Poor ●
Very Poor ●
Hazardous ●
0-33 34-66 67-99 100-149 150-200 200+

You can see the latest data readings on our Air quality in the ACT page.

Air Quality Index calculations

Data to calculate AQI values

Monitoring and reporting air quality starts with data from a network of air quality sensors and instruments that we manage at three sites across the ACT.

Data readings are actual measurements—numbers with measurement units, from scientific instruments for each air pollutant. Data is collected on five major pollutants.

The Air Quality Index (AQI) is a scale of air pollution over a designated time period that gives Canberrans an indication of how clean the air is so we can change our outdoor activities if pollution levels are high.

NEPM air quality standards used to calculate the AQI

Pollutant

Averaging period

Air NEPM Standard

PM2.5

24 hours

25 micrograms per cubic meter(µg/m3)

PM10

24 hours

50 micrograms per cubic meter(µg/m3)

Carbon monoxide

8 hours

9.0 parts per million (ppm)

Nitrogen dioxide

1 hour

0.08 parts per million (ppm)

Ozone

8 hours

0.065 parts per million (ppm)

Calculating the AQI

To calculate the index (AQI) values for each pollutant, the data reading is divided by the national standard and multiplied by 100 to get the AQI for the pollutant.
The formula is:

\[AQIpollutant = {pollutant data reading \over standard} \times 100\]

The ‘standard’ value in the formula for each major pollutant is specified by the Australian Government in the National Environment Pollution Measure (Ambient Air).

Understanding AQI for the site

The derived AQI values are a standardised set of values that ACT Health then compares and reports on. The highest AQI value for any pollutant at each site becomes the site AQI.

AQI values are interpreted by categorising them according to the air quality they describe. The resulting ratings, from very good air quality to hazardous, are labelled and colour-coded for easy interpretation.
An AQI of 100 or greater indicates that pollutant readings have reached or exceeded the relevant national standard.

Air Quality in the ACT

ACT Health reports on air quality using up-to-date, accurate data on levels of pollutants in the air. The Air Quality Index (AQI) displayed on this page provides a comparison of air pollutants, standardising measurements of ozone, carbon monoxide, nitrogen dioxide, and airborne particles in the environment in the ACT.

For health advice relating to air quality in the ACT, please refer to Air Quality Health advice Portal.

The Air Quality Index (AQI) readings on this page are updated with information calculated on data readings averaged over 1 hour for nitrogen dioxide, over 8 hours for carbon monoxide and ozone, and over 24 hours for particulates.

The figures represented below are averages over time, as prescribed by the NEPM standards. This means that if there is a sudden onset weather or smoke event (for example a dust storm or bush fire), it is possible that people will see the visible pollutant (smoke or dust) in the air before it starts to register on these graphs.

If this happens, ACT Health will assess the air quality and publish a public health alert, if required.

If you would like to see the grass pollen count for today and the next 6 days, visit the Canberra Pollen Count and Forecast Service. You can also download the AirRater app This free app provides users with up-to-date information on total pollen (including tree and grass pollens), smoke pollution and temperature in the ACT. Please note that pollen levels may vary between AirRater and the Canberra Pollen Count and Forecast Service from time to time. These differences arise because AirRater measures total pollens and Canberra Pollen Count and Forecast Service measures grass pollen only.

Page last updated on: 4 Oct 2022