The DewStop fan switch monitors humidity and dew point levels in a room and automatically switches the exhaust fan on or off to help minimize damage by lessening or stopping the growth of mold. DewStop's patent-pending Condensation Sentry is triggered when steam in the room becomes too heavy for the air to support, and the moisture then accumulates on surfaces like walls, mirrors and fixtures. It turns the fan on for 30 minutes or until the room is dry. The switch is easy to install and has a 30-minute timer and a manual on/off, or just rely on the DewStop sensor to do the job.