Use our general ventilation requirements chart to get an idea of how many air changes your space needs, and that information can be used to determine how much CFM your fan needs. CFM is the volume of air moved by a fan expressed in Cubic Feet per Minute. Air changes refers to the time required for a complete air change in a given space and normally expressed in minutes per change.

Several factors can affect air change such as a warmer climate, which will require more air changes per hour.  Larger spaces could require less frequent air changes.  Exercise caution if ventilating an area that contains hazardous fumes, gases or dust in the air.  Under these circumstances, specify a fan built for spark resistant construction.  This fan will include a cast aluminum propeller and a motor designed for hazardous locations.  Hazardous motors fall under several classifications so let us know specifically what is in the air so we can select the proper motor for your application.

All of our product pages have charts showing their CFM based on size and horse power.

SPACE TO BE VENTILATEDNO. OF AIR CHANGES / HR .NO. OF MIN./AIR CHANGE
Auditorium125
Bakeries203
Banquet Halls203
Boiler Room601
Bowling Alleys125
Cafeterias125
Churches125
Classrooms106
Cleaning & Drying125
Club Rooms125
Creameries106
Dance Halls125
Dining Rooms125
Dormitories106
Engine Rooms302
Factories106
Foundries125
Garages106
Kitchens302
Laboratories125
Laundries203
Lodge Rooms125
Machine Shop106
Mills125
Offices125
Packing Houses203
Plating Rooms203
Printing Plants154
Projection Booths601
Recreation Rooms125
Residences154
Restrooms125
Sales Rooms106
Ship Holds610
Stores125
Toilets203
Transfer Rooms203
Tunnels610

To determine the CFM needed for your general ventilation requirements, use the following formula:

CFM = [volume of space (WxHxL)] / [no. of minutes/air change]

INTAKE AIR:  Keep in mind, air will not efficiently exhaust without a proper source of intake.  The exhausted air must be replaced with fresh air.  Air intake velocity should be kept below 500 feet per minute (FPM).  To determine the minimum square feet of face area needed for intake, divide the CFM of the fan by the required velocity (CFM/Velocity = Area).