Leave home and let the fan run for as long as it needs to for exhausting moisture from the bathroom. The Delta Breez Signature VFB25ACH features a humidity sensor to determine when and how long should come on, based on the amount of humidity in the room. Once less than 60% humidity is detected, the fan will turn off. Toggle the wall switch to run the fan in normal mode at full speed. The choice is yours with this Delta Breez Signature 80 CFM humidity sensing bathroom exhaust fan.