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, five colour indicators are used to classify air quality as either '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.

By using the AQC colours and following general health recommendations stated in the activity guide below, you can take steps to limit your exposure to air pollution. For example, if the AQC at your local station is ‘Very Poor’ (red), the health advice in the activity guide can assist you in understanding how this might affect your health and recommend actions to take.

Some people are more sensitive to air pollution than others. Sensitive groups include people with heart or lung condition including asthma, people over the age of 65, infants and children, and pregnant women. The activity guide therefore has different recommendations for sensitive groups for each air quality category. General advice on actions you can take to protect yourself and your health at each colour category are also provided.

Air quality category

General health advice and recommended actions

Sensitive groups including:

  • people with a heart or lung condition, including asthma
  • people over the age of 65
  • infants and children
  • pregnant women

Everyone else

Good

  • NO CHANGE needed to your normal outdoor activities.
  • NO CHANGE needed to your normal outdoor activities.

Fair

  • REDUCE outdoor physical activity if you develop symptoms such as cough or shortness of breath.
  • Consider closing windows and doors until outdoor air quality is better.
  • Follow the treatment plan recommended by your doctor.
  • If you are concerned about symptoms call the 24-hour HealthDirect helpline on 1800 022 222 or see your doctor.
  • In a health emergency, call triple zero (000) for an ambulance.
  • NO CHANGE needed to your normal outdoor activities.

Poor

  • AVOID outdoor physical activity if you develop symptoms such as cough or shortness of breath.
  • When indoors, close windows and doors until outdoor air quality is better.
  • Follow the treatment plan recommended by your doctor.
  • If you are concerned about symptoms call the 24-hour HealthDirect helpline on 1800 022 222 or see your doctor.
  • In a health emergency, call triple zero (000) for an ambulance.
  • REDUCE outdoor physical activity if you develop symptoms such as cough or shortness of breath.

Very poor

  • STAY INDOORS as much as possible with windows and doors closed until outdoor air quality is better.
  • If you feel that the air in your home is uncomfortable, consider going to a place with cleaner air (such as an air-conditioned building like a library or shopping centre) if it is safe to do so.
  • Actively monitor symptoms and follow the treatment plan recommended by your doctor.
  • If you are concerned about symptoms call the 24-hour HealthDirect helpline on 1800 022 222 or see your doctor.
  • In a health emergency, call triple zero (000) for an ambulance.
  • AVOID outdoor physical activity if you develop symptoms such as cough or shortness of breath.
  • When indoors, close windows and doors until outdoor air quality is better.
  • If you are concerned about symptoms call the 24-hour HealthDirect helpline on 1800 022 222 or see your doctor.
  • In a health emergency, call triple zero (000) for an ambulance.

Extremely poor

  • STAY INDOORS with windows and doors closed until outdoor air quality is better and reduce indoor activity.
  • If you feel that the air in your home is uncomfortable, consider going to a place with cleaner air (such as an air-conditioned building like a library or shopping centre) if it is safe to do so.
  • Actively monitor symptoms and follow the treatment plan recommended by   your doctor.
  • If you are concerned about symptoms call the 24-hour HealthDirect helpline on 1800 022 222 or see your doctor.
  • In a health emergency, call triple zero (000) for an ambulance.
  • STAY INDOORS as much as possible with windows and doors closed until   outdoor air quality is better.
  • If you feel that the air in your home is uncomfortable, consider going to a place with cleaner air (such as an air-conditioned building like a library or shopping centre) if it is safe to do so.
  • If you are concerned about symptoms call the 24-hour HealthDirect helpline on 1800 022 222 or see your doctor.
  • In a health emergency, call triple zero (000) for an ambulance.

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 explainer diagram
  • 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 polllutant 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 (e.g. 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.

Monitoring and reporting air quality starts with data measurements from a network of air quality sensors and instruments at monitoring sites in New South Wales.

Data measurements readings are numbers with measurement units, from scientific instruments for each air pollutant. The measurement units for the different pollutants and visibility are in the table below.

Pollutant/Visibility Symbol Measurement unit

Ozone

O3

Parts per hundred million (pphm)

Nitrogen dioxide

NO2

Parts per hundred million (pphm)

Carbon monoxide

CO

Parts per million (ppm)

Sulfur dioxide

SO2

Parts per hundred million (pphm)

Particles - less than 2.5 micrometres diameter (small); less than 10 micrometres diameter (large)

PM2.5, PM10

Micrograms per cubic metre (µg/m3)

Visibility

Bsp

10-4 m-1

Data readings for pollutant and visibility measurements are then classified into air quality categories, using the respective cut-off values listed below. These provide pollutant AQCs, which summarise each pollutant measured at the site.

The resulting categories, from Good to Extremely Poor, are labelled and colour-coded for easy interpretation.

 



Air quality categories (AQC)

Air pollutant

Averaging period

Units

GOOD  

FAIR  

POOR  

VERY POOR

EXTREMELY POOR

Ozone
O3

1-hour

pphm

<6.7

6.7–10.0

10.0–15.0

15.0–20.0

20.0 and above

4-hour rolling

pphm

<5.4

5.4–8.0

8.0–12.0

12.0–16.0

16.0 and above

Nitrogen dioxide
NO2

1-hour

pphm

<8

8–12

12–18

18–24

24 and above

Visibility
Neph

1-hour

bsp

<1.5

1.5–3.0

3.0–6.0

6.0–18.0

18.0 and above

Carbon monoxide CO

8-hour rolling

ppm

<6.0

6.0–9.0

9.0–13.5

13.5–18.0

18.0 and above

Sulfur dioxide
SO2

1-hour

pphm

<13.3

13.3–20.0

20.0–30.0

30.0–40.0

40.0 and above

Particulate matter
< 10 µm PM10

1-hour

µg/m3

<50

50–100

100–200

200–600

600 and above

Particulate matter
< 2.5 µm PM2.5

1-hour

µg/m3

<25

25–50

50–100

100–300

300 and above

After we derive the pollutant AQCs air quality at a site or across regions can be summarised and compared.

  • To derive a 'Site AQC', all 'Pollutant AQC' at a single site are compared.
    The highest 'Pollutant AQC' becomes the 'Site AQC'.
  • To derive 'Regional AQC', all 'Site AQC' in a region are compared.
    The highest ‘Site AQC’ for a region becomes the 'Regional AQC'.