Air quality index
Air quality data tables display figures of hourly data. These figures are updated online regularly throughout the day.
The air quality index is calculated by converting the measured pollutant concentrations into index values. To generate the index values, pollutant concentrations are expressed as a proportion of the Air NEPM standards or EPP (Air) goals, and then placed in a category based on that index value.
Hourly air quality indices are available for South East Queensland, and the Gladstone, Mackay, Townsville, and Mount Isa regions. Index values make it easier to interpret current air quality in Queensland because they overcome the complexity associated with displaying pollutant concentrations.
There are five categories in the Department of Environment and Heritage Protection's Air Quality Index, ranging from very poor to very good. These categories are defined by index value ranges and colours as shown below.
| Not available | Very good 0-33 | Good 34-66 | Fair 67-99 | Poor 100-149 | Very poor >150 |
Calculating the air quality index
The concentration of a pollutant is measured by air quality monitoring equipment at a monitoring station. This pollutant concentration is then converted to an index value using the equation below.
The 'pollutant goal concentration' used to calculate the index value is the Air NEPM standard for that particular pollutant, or in the case of visibility, the EPP (Air) goal. The Air NEPM standards and EPP (Air) goals used in calculating the index value and the averaging times for the concentrations of the pollutants are presented below.
| Pollutant | Air NEPM standards | Averaging time |
|---|---|---|
| Ozone | 0.10 ppm | 1 hour |
| Nitrogen dioxide | 0.12 ppm | 1 hour |
| Sulfur dioxide | 0.20 ppm | 1 hour |
| Carbon monoxide | 9 ppm | 8 hour |
| PM10 | 50 µg/m3 | 24 hour |
| PM2.5 | 25 µg/m3 * | 24 hour |
| TSP | 80 µg/m3 ** | 24 hour |
Notes:
ppm: parts per million
µg/m3: micrograms per cubic metre
* NEPM Advisory Standard
** 'Good practice guide for assessing and managing the environmental effects of dust emissions'
| Pollutant | EPP(Air) goal | Averaging time |
|---|---|---|
| Visibility | 20 km | 1 hour |
The EPP (Air) goal for visibility-reducing particles is 20 km visibility, which means you would be able to see clearly for at least 20 km. This goal is related to a light scattering coefficient value measured using a nephelometer. The degree of scattering is inversely proportional to the visibility. A scattering of 235Mm-1 (Mm-1 per million metres) or less is equivalent to a visibility of more than 20 km. The visibility goal is designed to protect visual amenity, which means the distance that can be seen.
Once the index value is known, air quality is indicated by the colour and category value. Index values over 100 indicate that the pollutant concentration exceeds the air quality goal or standard. With the exception of visibility, the goals and standards are based on health studies and standards from around the world.
The one hour, eight hour and 24 hour averaging times are for the latest periods.