INSIGHT | VENTILATION
Above: Tunnel Giswil Exhaust Fans
Below: Jet Fan Maintenance
Two axial fans discharge the smoke through a vertical
outlet. The axial fans have a 2m-diameter and each has nominal power of 260kW. Four jet fans are installed in a 400m-long tunnel section at the southern portal. This section is not equipped for smoke extraction. The jet fans are controlled to switch on and off based on the measured airflow in the tunnel. In normal operation, the extraction system is used as a longitudinal ventilation with mid- point extraction. The daily traffic volume is about 11,000 vehicles per day with 3.5% heavy goods vehicles. Traffic is increasing as the connection allows residents to commute from the rural area to the city of Lucerne in the north. Tunnel Giswil has a parallel egress tunnel with seven
cross-connections to the traffic tunnel. The egress tunnel is equipped with a pressurisation system. It is designed for moderate overpressure in normal operation and an airflow of 1m/s in three simultaneously open egress
doors in emergency operation. The pressurisation system consists mainly of two axial fans and pressure relief dampers at the portals.
REFURBISHMENT PROJECT 2025 After 21 years of operation, some of the ventilation equipment reaches the end of its nominal design life: ● Control system ● Jet fans
● Smoke dampers ● Axial fans
15 years 20 years 25 years 30 years
The refurbishment project aims to renew and repair
the tunnel ventilation system to such an extent that safe operation can be expected until 2040. The measures must be financially viable and meet the goals of sustainability. In this project, this meant that changes to the civil
18 | January 2026
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