The purpose of ventilation in a road tunnel is to provide adequate fresh air and in the event of a fire, to control smoke.
Fresh air is provided through entirely automated systems, based on information from various sensors located throughout the tunnel (opacimeters, CO sensors, NOx sensors…).
For smoke extraction, the nature of the tunnel and in particular its level of surveillance (presence or not of a manned control centre 24/7), will dictate how the ventilation is controlled:
Each panel can activate smoke extraction, or stop it if required. In certain cases (reversible longitudinal ventilation system), the panels can also control the direction in which the smoke is blown.
If a smoke control panel is located at each portal, it is important to define which panel has priority over the other (for example, when the first panel is activated, it over-rides the second), in order to avoid contradictory commands if fire officers are located at both portals.