In enclosed tunnels smoke travels 200 m in a minute and temperature exceeds 1000 C (Mont Blanc 1999 - 39 dead, Kaprun 2000 - 155 dead). NFPA 502 governs ventilation, sprinklers, egress and passive structural protection in road, rail and metro tunnels.
Fire Load Classification
- Category I: Passenger car 5 MW
- Category II: Van 15 MW
- Category III: Truck 30-50 MW
- Category IV: Tanker 100-200 MW
- Metro train: 15-35 MW typical
Longitudinal Ventilation
- Jet fan: 40 kW every 100 m
- Critical velocity: 2.5-3.0 m/s backlayering
- Thrust: 1000-1500 N/fan
- Activation: Full speed within 90 s
- Temperature: 250 C 2 h fan run
Sprinkler and Water Mist
- Deluge density: 12.2 L/min/m2 road
- Zone: 30-50 m sector
- Activation: 60 s response
- Duration: 30 min minimum
- Water mist: 5-7 bar 100 micron
Egress and Structural
- Cross-passage: 250 m spacing metro
- Emergency exit: 300 m road
- Structural: RWS 2 h 1350 C concrete
- Passive: Perlite or vermiculite spray
- Fireproof cable: 30 min 750 C IEC 60331
Turkish Tunnel Examples
- Marmaray: 13.6 km + 76 m immersed
- Eurasia: 5.4 km Bosporus road
- Istanbul Metro M4-M7: NFPA 130 + 502
- Ankara M1-M4: 50 km total
- Canakkale 1915: Suspension bridge + 1.9 km tunnel
Tunnels with SprinkCalc
SprinkCalc sizes tunnel jet fan 1500 N thrust, 3 m/s critical velocity, deluge 12.2 L/min/m2, 250 m cross-passages and NFPA 502 layout.
Download SprinkCalc on the App Store
Sources & Further Reading
NFPA 502, NFPA 130, PIARC tunnel report, EU Directive 2004/54, RWS curve. NFPA 502 Road Tunnels and Highways.