# 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.

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 current air quality 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 0.12 parts per million (ppm) Ozone 1 hour 0.10 parts per million (ppm) 4 hours 0.08 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.

Page last updated on: 8 Jan 2020