Metro Tunnel Fire: NFPA 502 and Longitudinal Ventilation

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 (road tunnels) and NFPA 130 (metro and passenger rail tunnels, see NFPA 13-2025 27.23) govern ventilation, sprinklers, egress and passive structural protection.

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 to stop 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

• Undersea rail tunnel: 13.6 km, 76 m below sea level
• Undersea road tunnel: 5.4 km strait-crossing road
• Metropolitan metro lines: NFPA 130 + 502
• Another metro network: 50 km total
• A suspension bridge project: Suspension bridge + 1.9 km tunnel

MEP Calc — 110+ Engineering Calculators

MEP Calc bundles 110+ engineering modules in one iOS app: 21 fire calculations (sprinkler, fire pump, FM-200 clean agent) plus heating, cooling, HVAC, plumbing, steam and natural gas. Download it on the App Store.

Download MEP Calc on the App Store

SprinkCalc — Fire Sprinkler Design Across Three Standards

SprinkCalc covers hazard classification, design density and area, K-factor selection, water demand and hydraulic calculations for NFPA 13, FM Global and BS EN 12845 in a single iOS app, and exports a professional PDF report. One of the few tools that unifies all three major fire protection standards.

Download SprinkCalc on the App Store