"Axial Flow Fan", with the operation conditions of heat and changed to slow speed operation, the cooling fan will generate less noise and consumes less energy. In most of the design requirements, after cooling "Axial Flow Fan" hours of operation speed is lower than the air temperature is generally the maximum design temperature value. Under normal circumstances, low speed cooling fan can be enough to complete its work. However, when selecting and installing should also be considered: cooling fan temperature changes slowly, cooling fan speed changes are slow, will not suddenly change the cooling fan speed and noise. The reaction time depends mainly on the length of its heat-sensitive sensor sensitivity. So the heat "Axial Flow Fan" speed control speed automatically adjust based primarily on the temperature difference between the heat sink sensor passed.