Follow
Number of air changes/hour in an area is =Total Room Airflow in CFM x 60 / Total Volume of room in cubic feet
ACH = CFMx60/Room Volume
Example: Say the volume of the room is 1,200 cubic feet, and the volume of air the HVAC system is going to supply is 200 CFM. Thus, ACH = 200×60/1,200 = 10. This means the air is changed out 10 times per hour.
For calculating Total Room Airflow in CFM, first calculate air flow of individual filter.
Formula
Air flow (in CFM)=Avg. air velocity (in feet/Minute) x Effective area of filter
Then find Tatal air flow.
Formula is
Total Air flow=Sum of air flow of individual filter.
Air flow Velocity can be measured with the help of Anemometar
