Fans are used in ventilation systems to move the air by wires airspaces. The fan is necessary to overcome the resistance of the ventilation system created in pipes and fittings. This resistance creates pressure on the network. In calculating the net pressure necessary to choose a fan. The type of blades and operating principle of the fans are divided into the following groups: axial, radial, and diagonal fan.

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  Circular duct fan

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  Rectangular in-line duct fans

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  Foof fans