Air quality 

The RTA is committed to safely monitoring and managing air quality within Sydney’s tunnels, as well as nearby communities. Inside the tunnels, sophisticated measurement and ventilation systems ensure that air quality meets strict regulations governing emissions levels.

How the RTA manages air quality

Air quality in Sydney’s motorway tunnels is managed by flushing  the tunnel with fresh air. This dilutes the pollutants emitted from vehicles as they travel through the tunnel. Mixing large volumes of fresh air with the vehicle emissions ensures that the concentration of pollutants remain within set limits.
Fresh air is drawn into the tunnel portals by fans which also move the air along the tunnel at speed. In some tunnels additional fresh air is sucked into the tunnel using large fans at an air intake point.         

Once air has travelled along the tunnel it is expelled via a ventilation building. Typically, a ventilation building contains large fans which blow the tunnel air out at speed. The ventilation shafs are designed to ensure exhaust is well dispersed, this prevents pollutants from accumulating at ground locations.

Air quality in the Sydney Harbour Tunnel

The ventilation system in the Sydney Harbour Tunnel is as follows:

• Fresh air is injected into each tunnel by an air supply station through ducts located on the top or side of each tunnel.
• Air is moved through the tunnels by a combination of the movement of vehicles and jet fans.
• Tunnel air is then expelled through a ventilation shaft located in the northern pylon of the Sydney Harbour Bridge, and through the tunnel exits.