Ozone exceeded the national standard on 3 days. Ten stations recorded one day each above the standard.
The Bradfield Highway roadside air quality monitoring station in East Sydney exceeded the annual standard for nitrogen dioxide.
Carbon monoxide
The national standard for carbon monoxide (CO) is:
- 8-hour average – 9 parts per million (9 ppm).
Eight-hour carbon monoxide averages
No days exceeded the 8-hour CO standard in 2024.
The maximum 8-hour CO level of 2.5 ppm (28% of the national standard) was recorded at Macquarie Park in East Sydney, on 4 September 2024. This occurred following nearby hazard reduction burns.
Nitrogen dioxide
The national standards for nitrogen dioxide (NO2) are:
- 1-hour average – 8 parts per hundred million (8 pphm)
- annual average – 1.5 parts per hundred million (1.5 pphm).
One-hour nitrogen dioxide averages
No days exceeded the 1-hour NO2 national standard in 2024.
The highest 1-hour NO2 level was recorded at the Bradfield Highway roadside monitoring station (5.9 pphm, 74% of the standard, on 23 October 2024).
Annual nitrogen dioxide averages
Annual average NO2 exceeded the national standard at Bradfield Highway (1.9 pphm). This roadside monitoring station has been running since September 2018 and has exceeded the annual standard every year since 2019.
The next highest NO2 annual average was recorded at Cook and Phillip, located in the Sydney CBD (1.1 pphm, 73% of the standard).
Ozone
The national standard for ozone (O3) is:
- 8-hour average – 6.5 parts per hundred million (6.5 pphm).
Eight-hour ozone averages
Ozone levels peak in the warmer months from October to March.
There were 3 days in 2024 when the 8-hour ozone standard was exceeded, with 10 stations exceeding the standard on one day each as shown in the table below.
The most extensive ozone event occurred on 13 December when 6 stations across the wider Sydney region exceeded the standard. The maximum 8-hour ozone level in 2024 (7.5 pphm) was recorded during this event at Lidcombe in Central West Sydney.
Ozone levels remained below the standard in all other regions in 2024.
In 2023, the ozone standard was exceeded on 3 days, with 11 stations exceeding the standard on one day each.
Ozone exceedance summary
Value in brackets are the maximum 8-hour ozone levels at each station on the day in parts per hundred million (or pphm).
| Date | Station (maximum 8-hour ozone concentration, pphm) |
|---|---|
| 25/01/2024 | Newcastle (6.7) Wallsend (6.7) |
| 26/11/2024 | Camden (6.6) Campbelltown West (6.7) |
| 13/12/2024 | Earlwood (6.6) Lidcombe (7.5) Liverpool (6.7) Macquarie Park (7.0) Parramatta North (7.2) Prospect (7.3) |
Sulfur dioxide
The national standards for sulfur dioxide (SO2) are:
- 1-hour average – 10 parts per hundred million (10 pphm)
- daily average – 2 parts per hundred million (2 pphm).
One-hour sulfur dioxide averages
There were no days over the 1-hour SO2 standard in 2024. Morisset recorded the highest level (8.6 pphm) on 25 July.
In 2023, Muswellbrook in the Upper Hunter exceeded the standard on 2 days.
Daily sulfur dioxide averages
There were no days over the daily SO2 standard in 2024.
The maximum daily SO2 level (2.0 pphm) was recorded at Muswellbrook on 5 June 2024, just meeting the standard.
In 2023, one day at Muswellbrook exceeded the standard.