Smoke Damper Sizing Calculator

Calculate smoke damper size per NFPA 105 based on duct airflow, velocity limits, and leakage class

Input Parameters

Results

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Min Damper Free Area
ft2
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Actual Face Velocity
ft/min
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Max Leakage Rate
CFM
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Recommended Damper Size
Note: NFPA 105 requires smoke dampers at penetrations of smoke barriers. Class I dampers are required for most smoke control applications. UL 555S listing required. Consider elevated temperature rating for dampers in smoke exhaust systems.

Reference

NFPA 105 Smoke Damper Sizing: Min Area = CFM / Max Velocity Damper Area >= Duct Area Leakage: Class I = 8 CFM/ft2, Class II = 20 CFM/ft2, Class III = 80 CFM/ft2 All leakage ratings at 1 in. w.g. differential Face velocity typically limited to 2000 ft/min