As per American
Society of Mechanical Engineers
(ASME) the specific ratio - the
ratio of the discharge pressure
over the suction pressure – is
used for defining the fans,
blowers and compressors
Fans - Up to 1.11
Blowers- 1.11 to 1.20
Compressors - more than 1.20
fan is just used for air moving.Its blade are axailly bladed.
fans usually move large volumes of air at low pressure.
blower is a centrifugal fan,blower is a machine for moving
volumes of a gas with moderate increase of pressure.