With "Air Purifier Fan" application and ambient temperature changes, and sometimes require different speed fan to meet demand. Some manufacturers specially designed adjustable fan speed cooling fan, manual and automatic modes. Manual "Air Purifier Fan" is designed to allow users to use low-speed low-noise in the winter, using high-speed access to good cooling effect in the summer. Usually automatic type provided with a radiator thermostat thermostat sensor to automatically control the fan speed based on the current operating temperature, the temperature is high, the rotational speed is increased, the temperature is low, the reduced speed to achieve a dynamic balance, so that the "Air Purifier Fan "cooling effect of wind noise and maintain an optimal combination of points.