Fans can be divided into several types according to the material used, such as iron shell fans (common fans), glass steel fans, plastic fans, aluminum fans, stainless steel fans and so on. 
In the direction of gas flow
Fan classification can be divided into centrifugal, axial flow, diagonal flow (mixed flow) and cross flow types according to the direction of gas flow.
(1) Centrifugal fan. After entering the impeller of the fan axially, the airflow mainly flows in the radial direction. This type of fan is made according to the principle of centrifugal action. The products include centrifugal fans, centrifugal blowers and centrifugal compressors. 
(2) Axial fan. The airflow enters the impeller of the fan axially and flows approximately along the axis on a cylindrical surface. Such fans include axial flow fans, axial flow fans and axial flow compressors.
(3) Swing fan. Rotate the rotor to change the volume of the air chamber to work. Common varieties are Roots blowers and rotary compressors.
Fans are divided into axial flow fans, centrifugal fans and diagonal flow (mixed flow) fans according to the flow direction of the airflow after entering the impeller.
Fans are divided into press-in local fans (hereinafter referred to as press-in fans) and explosion-proof motors located outside or in the flow channel, and explosion-proof motors are located in the explosion-proof sealed cavity withdrawable local fans (hereinafter referred to as withdrawable fans ).
Fans can also be divided into single-stage, double-stage or multi-stage pressurized fans according to the pressurized form. For example, 4-72 is single-stage pressurization, and high-end fans are multi-stage pressurized fans.
Fans can be divided into axial fans, mixed-flow fans, roof fans, and air-conditioning fans according to their applications.
Fans can be divided into negative pressure fans, low pressure fans, medium pressure fans, and high pressure fans by pressure.
According to the outlet pressure (boost), it is divided into: ventilator (≤15,000 Pa), blower (15,000 to 350,000 Pa), compressor (≥350,000 Pa) .
Sort by layer
There are many classification methods for fans, which can be roughly classified according to the following layers:
(1) According to the level of pressure, it can be divided into: volumetric type: reciprocating and rotary type; turbine type: centrifugal type, axial flow type, mixed flow type and cross flow type, jet type.
Ventilator generally refers to the turbine type, that is, centrifugal, axial flow, mixed flow, cross flow and other forms. 
Its main features are:
Centrifugal fan: higher pressure, but smaller air volume.
Axial fan: higher air volume, but lower pressure.
Mixed flow fan: The air volume and pressure are between the centrifugal and axial flow fans.
Cross-flow fan: It has high dynamic pressure and can obtain flat airflow.
(2) It can be divided according to the material used; iron shell fan (common fan), glass steel fan, plastic fan, aluminum fan, stainless steel fan, etc.
(3) According to the direction of gas flow, it can be divided into: centrifugal type, axial flow type, diagonal flow type (mixed flow type) and cross flow type.
(4) According to the flow direction of the airflow after entering the impeller, it can be divided into: axial flow fan, centrifugal fan and diagonal flow (mixed flow) fan.
(5) According to the application, it can be divided into: a push-in local fan and an explosion-proof motor placed outside or in the flow channel, and the explosion-proof motor is placed in the explosion-proof sealed cavity withdrawable local fan.
(6) According to the form of pressurization, it can also be divided into: single-stage, double-stage or multi-stage pressurized fans.