Once rail and metro tunnels exceed 1 km with limited exits, egress suddenly becomes a life-critical issue. NFPA 130 (Fixed Guideway Transit and Passenger Rail Systems) provides the framework for fixed fire fighting systems (FFFS), longitudinal ventilation and evacuation times. The notes below draw on large tunnel projects.
HRR Scenarios
- Metro car: 7-10 MW (EN 45545-2 R1-R24 class)
- Freight car: 50-100 MW (Channel Tunnel HGV shuttle)
- TGV/Velaro: 15-25 MW
- Peak HRR duration: 10-15 min; design verified by CFD
Longitudinal Ventilation
- Critical velocity: 2.5-3 m/s (prevents backlayering)
- Jet fan: every 100 m, 2 x 250 kW
- Portal fan: large fans at tunnel mouth
- Smoke damper: zone isolation
- CFD: Froude + Richardson number validation
Water Mist FFFS
- High pressure: 100 bar, 1 L/min/m² application rate
- Nozzle spacing: 3 m longitudinal, 2.5 m transverse
- Activation: linear heat detection + CCTV
- Zone: 200 m sections, only one zone active at a time
- Water reserve: about 200 m³ (10 m³/min × 20 min)
Egress Route
- Cross passage: every 250 m connecting twin tubes
- Pressurization: cross passage +50 Pa
- Walkway: rail level, 1.2 m width
- Emergency light: LED, 90 min battery, 10 lux
- Evacuation time: 10-15 min target for 1,000 passengers in a 2 km tunnel
International Examples
- Channel Tunnel: 50.5 km, FFFS added after 1996 fire
- An undersea rail tunnel: 13.6 km, FFFS + twin portal fans
- An undersea road tunnel: 5.4 km, 2x2 lane road - NFPA 502
- Gotthard Base Tunnel (Switzerland): 57 km, jet fans + fixed water spray
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Download SprinkCalc on the App StoreNFPA 130, NFPA 502, PIARC Road Tunnel Guidelines, EN 45545 Fire Safety Rail. NFPA 130 Rail Transit standard.