The SmartExhaust™ is designed as a replacement for the bathroom fan and light switch, helping insure healthy indoor air quality as well as adequate bathroom ventilation. By using a microprocessor to monitor and control fan operation, a precise amount of ventilation can be provided. There are two settings on the SmartExhaust™ switch, ventilation and delay. Ventilation is the minutes per hour that you want the fan to operate. Delay is the number of minutes you want the fan to run after the bathroom light has been turned off. The delay time provides additional run time of the fan to complete ventilating the bathroom after use. When a person enters the bathroom and turns on the light, the fan is also energized. After the person leaves the bathroom and turns the light out, the fan continues to run for the set delay time. In addition once an hour the fan is energized for the set ventilation time. What makes this switch particularly unique is that the microprocessor monitors manual operation time and Delay time and subtracts it from the set hourly ventilation time. For example, with a 20 minute Ventilation setting and a 10 minute delay setting, a person enters the bathroom and uses it for 5 minutes. The fan will continue to run for another 10 minute delay time. That totals 15 minutes of run time for that hour. The microprocessor will subtract that 15 minutes of operation from the 20 minute set ventilation time and at the end of the hour, the fan will only run for 5 additional minutes.