Between 2008 and 2020, air quality data in New South Wales was presented using the Air Quality Index (AQI). It was replaced by the current Air Quality Categories (AQC) in November 2020 to provide more detailed health information and clarity on ambient air quality levels.
The AQI was, like any other index, a number. Just as the ASX200 index allows investors to understand the strength of the Australian stockmarket, so the air quality index (AQI) helped us to understand air quality. The ASX200 is calculated from the values of 200 selected Australian shares. Likewise, the AQI was calculated from air quality data for 5 pollutants and visibility readings.
What the AQI numbers meant for you
For each pollutant, the Air Quality Index (AQI) was the data value expressed as a percentage of the level specified by the National Environment Protection Measure for Ambient Air (NEPM) standard (or, in case of visibility, of the relevant NSW standard). An AQI of 100 corresponded to the NEPM national standard, and levels at or above 100 signified 'Poor' air quality.
A lower value indicated better air quality and a higher value, worse.
The AQI comprised of 6 categories and provided more limited health information than the current AQC. The AQC has 5 categories.
AQI |
What action should people take? |
Very good |
Enjoy normal activities |
Good |
Enjoy normal activities |
Fair |
People unusually sensitive to air pollution should reduce or reschedule strenuous outdoor activities. Others are not likely to be affected when the AQI is in this range. |
Poor |
Sensitive groups should reduce strenuous outdoor activities. Other adults are not likely to be affected. Anyone who experiences symptoms should reduce outdoor activities. |
Very poor |
Sensitive groups should avoid strenuous outdoor activities Other adults should reduce or reschedule strenuous outdoor activities. |
Sensitive groups should avoid all outdoor activities. Other adults should avoid strenuous outdoor activities. |
Steps to calculate AQI values
Because data readings have different underlying units of measure, it is difficult to compare the various pollutants. AQI values were calculated from data to have a standardised set of numbers to compare and share. The AQI was calculated using the following steps: