Centrifugal fans or blowers use one of seven types of wheels that
are enclosed in a scroll shaped housing. The air enters the fan
wheel through the housing inlet, turns 90 degrees and is
accelerated radially and exits the fan housing.
Axial fans use a propeller, having two or more blades, to move air
in an axial direction through a cylindrical housing or formed
The term fan is used to describe either a fan or blower. To make
the proper fan selection, you must consider the following
conditions the fan will be subjected to:
What is the air volume that will be required? This is rated in
cubic feet of air per minute (CFM) or the metric equivalent, cubic
meters per hour (M3/Hr).
What is the static pressure resistance through the complete system?
This is rated in inches water gauge (in WG) or the metric
equivalent, millimeters water gauge (mm WG).
Note: in WG or mm WG is the resistance to flow, or friction, caused
by the air moving through a pipe or duct. Be sure to include other
such as filters, dampers, heat exchangers, etc.