Calculate Air Changes Per Hour (ACH)

Enter in the following:

Total Room Area (Sq ft)

Ceiling Height (ft)

Airflow (CFM)

???? ACH

Formula and Explaination

Flowrate of Air / (Total Volume of space)

For a 10ft by 20ft by 10ft cleanroom with 600CFM of airflow, there would be 18ACH. To put that in persective, that would mean the air is changed out 18 times per hour.

When designing and commisioning new air systems, it is important to understand how many air changes are taking place. A greater number of air changes per hour helps eliminate odors and fumes quickly and can provide fresh air for combustion or filtered air for aseptic processing.

Recommended Air Change Rates

Residential

ASHRAE reccommends 5 ACH for a kitchen to provide enough ventilation for smoke, smells, and combustion from gas appliances.

Hospital Rooms

For airborn infectious isolation rooms used for COVID-19 or other contagious diseases are recommended to have 6 to 12 ACH.

Pharmaceutical Clean Rooms

For an ISO grade clean rooms:

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