In Tunnel Air
In-tunnel air quality
In-tunnel air quality for the safety of motorists is ensured through the continuous monitoring of Carbon Monoxide (CO) and Nitrogen Monoxide (NO) as well as visibility.
The key factor influencing in-tunnel air quality is the emissions that are generated by the traffic using the tunnels. These vehicle emissions are affected by a number of factors such as the speed at which the traffic is travelling, the mix of vehicle types and the fuel used by those vehicles. In-tunnel air quality is also influenced by a number of other factors, including the quality of exhausts from vehicles, and the velocity of air moving through the tunnels.
The control of air quality within the tunnel is achieved by adjusting the numbers of fans to enable the rate of air flow through the tunnel to be varied according to the level of emissions in the tunnel. In essence, the higher the level of emissions in the tunnel, the higher the rate of air flow required in order to maintain an acceptable in-tunnel air quality. The tunnel ventilation system enables the specified in-tunnel air quality requirements to be met under all credible atmospheric and traffic flow scenarios.