The remarkable DewStop product is constantly checking the air for condensation. At the right time, DewStop will turn ON your fan and run to clear the room. Replace your existing fan switch with DewStop and your fan is now a smart fan. DewStop's sensors are always watching for harmful moisture, ready to control your fan when your family forgets to. With its built-in sensor, it constantly monitors the air for condensation and triggers the fan on to clear the room & keep it dry. Versatile-can be used in bathrooms, laundry rooms, sunrooms, spa rooms and in all condensation areas of the home.