Goals and limits

Monitoring types

The air quality goals and criteria for pollutants monitored at the WestConnex tunnel ambient monitoring sites are based on the following Conditions of Approval: 

The air quality goals and criteria are shown in the table below:

Monitoring typePollutant / parameterAveraging periodUnits of measurementLimit / goal
External ambientCO8 hours (rolling)PPM9
External ambientNO21 hourPPM0.125
External ambientPM2.524 hoursµg/m³25
External ambientPM1024 hoursµg/m³50
External ambientSigma Theta1 hourºN/A
External ambientTemperature at 10 metres1 hourKN/A
External ambientTemperature at 2 metres1 hourKN/A
External ambientWind direction1 hourºN/A
External ambientWind speed1 hourm/sN/A
In-tunnelCO3 minutes (maximum value)PPM200
In-tunnelCO15 minutes (maximum value)PPM87
In-tunnelCO30 minutes (maximum value)PPM50
In-tunnelNO215 minutes (maximum value)PPM0.5
In-tunnelVisibility15 minutes (maximum value)m-10.005
Ventilation outletCO1 hourmg/m³40
Ventilation outletNO21 hourmg/m³2
Ventilation outletNOX1 hourmg/m³20
Ventilation outletSolid particles1 hourmg/m³1.1
Ventilation outletVOC1 hourmg/m³4

Traffic light status

We have developed a traffic light status for air quality based on the same values the Office of Environment and Heritage (OEH) use to display their Air Quality Index (AQI). The AQI is a scale of air pollution that helps people understand air quality and modify any activities if pollution levels are high. For further detailed description and explanation of the OEH AQI visit Understanding air quality for the Office of Environment and Heritage.

The traffic light status of each pollutant is shown in the 'Current snapshot' table for External Ambient, In-tunnel and Ventilation Outlet and it is based on the hourly reading relative to the limit or goal.

Percentage of goalTraffic light status
If reading is less than 67% of limit/goalGood
If reading is greater than or equal to 67% and less than 100% of limit/goalFair
If reading is greater than or equal to 100% of limit/goalPoor