Tunnel Fire Critical Velocity & Smoke Backlayering Calculator
Determine the minimum longitudinal airflow velocity ($v_c$) to prevent upstream smoke backlayering during tunnel emergencies per NFPA 502 and the Kennedy / Oka-Atkinson equations.
Fire Heat Release & Tunnel Profile
Positive = uphill slope
Critical Velocity & Ventilation Airflow
Critical Velocity (v_c)
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Required Volumetric Airflow
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Grade Factor K_g
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Hot Gas Temp T_f
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Froude Number Fr
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NFPA 502 Life Safety Compliance
Smoke layer will be swept downstream, ensuring clear upstream evacuation path.
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