Fan Control. The DewStop bath-fan control by GTR Technologies monitors air for high humidity and activates the room’s exhaust fan as needed. Once it’s been triggered by condensation, the switch stays on for 30 minutes after the room is dry. The fan can also be operated manually. It costs about $60; a model that controls lights, too, costs $70. GTR Technologies, 360/876-2974, dewstop.com.