HVAC & Ventilation
Required Air Flow Rate
Calculate the required ventilation air flow rate based on room volume and desired air changes per hour (ACH), or based on occupancy.
Units:
Offices typically require 6–10 ACH or 8–12 l/s per person. Industrial spaces 10–30 ACH. Clean rooms 60–600 ACH. EN 15251 defines ventilation categories.
Q [m³/h] = V [m³] × ACH [1/h]
Input
Room volume V iRoom volume = length × width × height in m³.
m³
Air changes per hour ACH iRequired air changes per hour. Office: 6–10, Kitchen: 20–30, Industrial: 10–30 ACH.
1/h
Number of persons iFor occupancy-based calculation. EN 15251 Category II: 7 l/s per person.
Fresh air per person iFresh air supply per person. EN 15251: Cat I = 10 l/s, Cat II = 7 l/s, Cat III = 4 l/s.
l/s/person
Result
Flow based on ACH [m³/h]
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Flow based on ACH [l/s]
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Flow based on occupancy [m³/h]
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Design flow (use higher) [m³/h]
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