suction fan It is a type of integral fan with a large space inside the mechanical chamber. During operation, there will be a lot of gas in the chamber, and the amount of air delivered can be controlled. The mechanical speed is proportional to the air volume. The main reason is due to the small gap between the impeller end face and the front and rear end covers of the fan, as well as the small clearance maintained by the fan impeller, which allows air to circulate.