Fan

A fan, comprising:

• a frame comprising an inlet, an outlet, a first accommodation space, a base and a second accommodation space, wherein the inlet and the outlet are disposed at opposite sides of the frame and in fluid communication with each other through the first accommodation space, and the first accommodation space is separated from the second accommodation space;
• an impeller disposed in the first accommodation space and on the base;
• and
• a driving assembly disposed between the base and the impeller;
• and
• a circuit board disposed in the second accommodation space,
• wherein the base comprises a plurality of first through holes, and the impeller comprises a plurality of second through holes;
• wherein when the fan is operating, a first airflow is formed to flow from the inlet to the outlet, and a second airflow is formed to flow through the driving assembly via the plurality of first through holes and the plurality of second through holes;
• and
• wherein a ratio of a distance between the plurality of second through holes and a top surface of the impeller to a height of the impeller is ranged from 0.2 to 0.6.