In tunnels of about 3 km in length, 1400mm diameter fans are used. One fan is installed in the tunnel tube axis.
In tunnels up to 1000 m in length, 1250 mm diameter fans are used. The installation is carried out with one or two fans in pairs or one in the tunnel tube axis.
There are no fans installed in tunnels below 500 m. Vibration sensor is installed on all fans.
In all tunnels with a ventilation system, the following process sensors are used:
- Fog detector in front of tunnel portals,
- CO level meter and tunnel visibility meter,
- Measurement of the intensity and direction of air flow in the tunnel.