Makeup Air Requirements Calculator

Calculate makeup air requirements for smoke exhaust systems to maintain pressure balance

Input Parameters

Results

--
Makeup Air Required
CFM
--
Min Opening Area
ft2
--
Net Exhaust (negative pressure)
CFM
--
Estimated Fan HP
HP
Note: NFPA 92 recommends makeup air between 85-95% of exhaust rate. Makeup air velocity at openings should not exceed 200 ft/min to avoid disturbing the smoke layer. Locate makeup air inlets at low level below the smoke layer.

Reference

NFPA 92 Makeup Air: Makeup CFM = Exhaust CFM x Makeup % Net Exhaust = Exhaust - Makeup (creates negative pressure) Min Opening Area = Makeup CFM / Max Velocity Fan HP = (CFM x SP) / (6356 x Efficiency)