Understanding air quality data

Air pollution has a significant impact on human health and the economy. However, air quality in New South Wales is usually very good by international standards. It is important to protect your health when air quality is poor by modifying your activities. You can find out about how current air quality might affect your health by looking at the colour indicator of the Air Quality Index (AQI).

The Department of Planning, Industry and Environment and NSW Health created the colour indicator scale to provide advice on what activities you can do, based on what the AQI is in your area. This enables you to protect your health during poor air quality events.

For a broader picture of air quality in New South Wales, you can download NSW Annual Air Quality Statements and NSW Annual NEPM Compliance Reports.

The Air Quality Index (AQI) rating is a scale that helps us understand how clean or polluted the air is across New South Wales, and how current air quality might affect your health.

In the national standards, different air pollutants have different thresholds for human health. To create the Index, each pollutant’s threshold is set at 100. For example, an AQI rating of 150 means that the pollution level in that area is 1.5 times the national standard and is flagged with the colour indicator for ‘Very Poor’.

The AQI reports on five air pollutants and visibility. It provides standardised measures of:

  • ozone
  • carbon monoxide
  • sulfur dioxide
  • nitrogen dioxide
  • airborne particles (such as PM10, PM2.5)
  • visibility.

Visibility is a good indicator for smoke. While visibility is affected by dust, the instrument is more sensitive to smoke.

The AQI provides information on how the current air quality in an area may affect your health. AQI readings are updated hourly, and viewable on this map of NSW and in the AQI table.

We also predict the AQI for the Greater Sydney Region, and a daily air quality forecast is issued at 4pm every day.

The AQI ratings use a colour indicator scale to provide health information.

The colour indicators come with advice from NSW Health on how to modify your activities if pollution levels are high. If you are not sure about what the numbers mean, don’t worry: all you need to do is follow the health advice for the colour indicator. For example, if the AQI exceeds 200, air quality is rated as ‘hazardous’ and sensitive groups must avoid any outdoor physical activity, while everyone else should significantly cut back on outdoor activity.

A rolling average is an average of the previous hours leading to the hour in question. In the case of a rolling 24-hour average, the previous 24 hours leading to the hour in question are used.

For reporting on particulate matter, our AQI calculations use a rolling 24-hour average because we are required to report 24-hour averages to the Australian Government under the National Environment Protection (Ambient Air Quality) Measure.

If you would like to get an hourly picture of PM2.5 levels, just look at the Visibility (NEPH) column in the AQI data table, as this measurement correlates to PM2.5.

For an animated graph demonstrating a rolling average, go to our alerts explainer.

When it’s smoky, everyone should:

  • Follow your doctor’s advice about medicines and your asthma management plan if you have one. Keep your medication close at hand. Consult your doctor if symptoms worsen.
  • Reduce or avoid vigorous outdoor activity see activity guide below.
  • Spend more time indoors. Keep doors and windows shut to keep the smoke out. Open windows and doors whenever the smoke clears.
  • Spend time in air conditioned venues like cinemas, libraries and shopping centres.
  • Avoid indoor sources of air pollution like cigarettes, candles and incense sticks.​​​​​

Anyone with persistent symptoms should seek medical advice or call Health Direct Australia on 1800 022 222.