How many ACH do I need?

Office:4-6, Kitchen:12-20, Warehouse:4-8, Lab:8-15, Hospital:6-12.

What is an air change?

Replacing entire room volume once. 6 ACH=6 replacements per hour.

1 CFM=1.699 m³/h. Divide m³/h by 1.699.

Calculate based on exhaust. Supply=exhaust ±10%.

No. Filter ΔP affects fan sizing but not ACH calculation.

Free Engineering Tool — #158

Q=V×ACH/60. Calculate fan flow from room volume and air changes per hour.

Q=V×ACHm³/h & CFM

Required Flow Rate

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Flow (CFM)

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Room Volume

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Flow (L/s)

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