The ventilation of rail and subway tunnels has become one of the focal points in any tunnel project. Several accidents have rendered regulations stricter.
In road tunnel projects, beginning in the year 2000 the focus has shifted from fresh air supply to control of smoke propagation in an emergency.
While ensuring a high safety level and system availability, there is always substantial pressure to reduce costs during all phases of the project, i.e. the planning, the realization and the operation.