Tunnel air quality

NorthConnex is a nine kilometre tunnel linking the M1 Pacific Motorway at Wahroonga to the Hills M2 Motorway at West Pennant Hills. NorthConnex is one of the longest and deepest road tunnels in Australia, removing around 5,000 trucks off Pennant Hills Road each day. NorthConnex is operated in accordance with the Conditions of Approval established by the NSW Government and approved by the NSW Minister for Planning.

Monitoring and measuring protocols for each pollutant and parameters are described in the glossary of terms.

The in-tunnel air quality monitoring shows data for:

  • Carbon monoxide (CO)
  • Nitrogen dioxide (NO2)
  • Visibility (K)

Air Quality in NSW, particularly visibility and particle concentrations, may be impacted from both natural sources (such as weather, fires or dust storms) and human activities. We encourage you to visit NSW Office of Environment and Heritage website for a daily update on Sydney’s current and forecast air quality.

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The external ambient air quality monitoring shows data for:

  • Carbon monoxide (CO)
  • Nitrogen dioxide (NO2)
  • Particles less than 2.5 micrometers in diameter (PM2.5)
  • Particles less than 10 micrometers in diameter (PM10)
  • Standard deviation in wind direction (Sigma theta)
  • Temperature at 2 metres (ºC)
  • Temperature at 10 metres (ºC)
  • Wind direction (degrees)
  • Wind speed (m/s)


External ambient data is monitored and published by Ecotech. 

Live external ambient data can be viewed here.


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The data used in the compilation of this page has undergone only preliminary quality assurance checks. This data must be preliminary until a monthly quality assurance check / validation process has been undertaken by a person or organisation accredited by the National Association of Testing Authorities (NATA). For further detailed description and explanation of the quality assurance and data validation process, visit the Office of Environment and Heritage.

Validated data will become available on this page approximately one month after the end of the calendar month. For example, the January data which has been validated will become available at the end of February. Validated air quality data reports are published monthly on this page.

If you require more information or have questions about our site's disclaimer, please feel free to email us.