The main function of a computer fan is to remove heat and replace it with fresh air into the system. This cooling fan has been designed to be suitably placed on the motherboard or hard disk drive. There are about 3 or 4 fan blades on the CPU. 

There are also computers that have been specifically designed to have an extra fan attached to a computer case made of aluminum, however, the fan is not enough to reduce the heat generated by the CPU so the CPU cooling fan must be installed, especially for computers that are used between 12 up to 15 hours a day so that the fan will not be enough to provide adequate air ventilation. Therefore the cooling fan for the CPU is designed and has been proven to be able to reduce heat generated by the CPU even though the computer is operated for a long time.