Air changes per hour explained
What ACH means
ACH is the hourly airflow divided by room volume.
Formula
ACH = CFM × 60 ÷ room volume
Interpretation
ACH does not guarantee perfect mixing or indicate whether the flow is outdoor air, exhaust, or filtered recirculation.
FAQ
Is one ACH a complete air replacement?
It is a volume-flow rate, not a guarantee of complete mixing.