Abstract: A pump includes a DC motor (10) defining a chamber (108) and having a rotor (112) and a shaft (110) suitably received in the chamber, a motor shell (20) set around the DC motor, a rear cover assembly (30) jointed to the motor shell, a front cover assembly (40) secured to the rear cover assembly, and a check valve assembly (50) and a diaphragm assembly (60) set between the front cover assembly and the rear cover assembly. The DC motor defines a number of air inlets (116) and air outlets (118) at two side walls (104, 106) thereof, respectively. The shaft is equipped with a rotatable fan (10). The motor shell has a number of ventilation holes (200) in communication with the air outlets. The rear cover assembly defines a number of through-holes (300) communicated to the air inlets. The through-holes, the air inlets, the chamber, the air outlets and the ventilation holes jointly define an air flow path.