Fan

A fan comprising:

• an impeller including a boss and a plurality of blades, the boss having a columnar shape and being driven to rotate by a motor, the plurality of blades being provided radially from the boss;
• an air guide portion through which an airflow moves from one end to an other end of the air guide portion, the air guide portion having a cylindrical shape and being provided to cover an outer peripheral end of each of the plurality of blades;
• and
• a bell mouth having an annular shape, the bell mouth being provided to extend, to a position that is upstream from the one end of the air guide portion, from a position that is downstream from the one end of the air guide portion and that is upstream from the impeller, the bell mouth defining a first suction passage inside the bell mouth and defining, together with an inner surface of the air guide portion, a second suction passage outside the bell mouth,
• between an upstream end point located in an inlet of the first suction passage and a downstream end point located in an outlet of the first suction passage of the bell mouth, the bell mouth including a minimum possible radius point to which a distance, in a radial direction, from a rotation axis of the boss is smaller than a distance, in the radial direction, from the rotation axis to the downstream end point.