Mechanical Smoke Exhaust Calculator

Calculate mechanical smoke exhaust CFM requirements based on fire scenario and space geometry

Input Parameters

Results

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Required Exhaust
CFM
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Mass Flow Rate
lb/s
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Smoke Layer Temp
F
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Est. Fans (15000 CFM ea)
Note: Mechanical exhaust fans must be rated for the expected smoke temperature (typically 250-600F). UL 762 rated smoke exhaust fans are required. Size fans with redundancy - NFPA 92 requires system to function with largest fan out of service.

Reference

Mechanical Exhaust per NFPA 92: m_dot = 0.071*Qc^(1/3)*z^(5/3) + 0.0018*Qc (kg/s) Qc = 0.7 * Q (convective HRR) V_dot = m_dot / rho_smoke CFM = V_dot(m3/s) x 2118.88 Smoke Temp = T_amb + Qc/(m_dot * Cp)