A NSW Government website

About the air quality categories

Air quality categories help us understand air quality and modify our activities if pollution levels are high.

 

Air quality categories (AQC) are colour indicators used to summarise air quality measurements. In New South Wales, 5 colour indicators are used to classify air quality as 'Good', 'Fair', 'Poor', 'Very Poor' or 'Extremely Poor'. 

The AQC is determined by measurements of key air pollutants we monitor at our monitoring locations:

  • particles less than 2.5 micrometres diameter (PM2.5)
  • particles less than 10 micrometres diameter (PM10)
  • ozone
  • nitrogen dioxide
  • carbon monoxide
  • sulfur dioxide
  • visibility.

The AQC is reported for each station, and for each region comprising the New South Wales Air Quality Monitoring Network. Details on how monitoring data are used to derive the AQC are in the tab below.

What the air quality categories mean for you

The AQC colours provide at-a-glance information to help people plan their activities, as shown in the Environmental Health Standing Committee's (enHealth) activity guide below.

How air quality categories are derived

The graphic below shows air quality category (AQC) colours, which are summarised at the pollutant, site and regional level.

Air quality categories chart explained in text on this page

The graphic shows air quality category (AQC) colours, which are summarised at the pollutant, site and regional level.

  • Pollutant AQC categorises each pollutant measured at a site with one of the 5 colour codes. The colour code is determined by comparing the hourly measurement for each parameter against the cut-off values listed below (select the 'Categorise air pollutant measurements' accordion). 

    In the graphic above, PM10 at Bringelly is colour-coded orange ('Poor' air quality) as the hourly measurement for PM10 falls in the 'Poor' category. Hourly measurements of visibility and PM2.5 are categorised as 'Fair' (yellow) based on their respective cut-offs, while all other parameters are 'Good' (green). 

  • Site AQC summarises air quality for a site, by comparing all pollutants measured at the site. It is determined from the highest category when comparing all pollutant AQCs at a site. In the graphic above, the highest category at Bringelly site is colour-coded orange, due to PM10, which corresponds to 'Poor' air quality. 
  • Regional AQC summarises air quality for each region (for example, Sydney South-west). It is determined by the highest site AQC when comparing all sites across a region (hence each region has a colour-coded regional AQC). In the graphic, Regional AQC for Sydney South-west is colour-coded orange because at Bringelly station air quality is 'Poor' due to PM10 and has the highest site AQC when compared to other stations in the region.