A sensor in a bathroom continuously senses the humidity level therein at periodic intervals and provides the sensed humidity values to a processor, which stores the sensed values and continuously calculates an average humidity value over a time period. The processor continuously checks if the current sensed value exceeds an upper threshold value related to the calculated average humidity value and, if so, turns on an exhaust fan. Once the upper threshold value has been exceeded, the processor continuously checks if the current sensed value has dropped below a lower threshold value related to the calculated average humidity value and, if so, turns off the exhaust fan and, if not, leaves the exhaust fan on for a period of time. If the processor is not controlling the exhaust fan in the on position, a user can manually activate a switch to turn on the exhaust fan for a certain period of time.