DewStop FS-300-W1 Adjustable Fan Humidity Control Switch with Adjustable Timer (White) Adjustable condensation sensors turn bath fan on when condensation is present and off when dry Blue LED light indicates the bath fan is on Moisture sensors prevent the growth of mold by triggering ventilation Includes adjustable condensation sensor and adjustable fan timer Manual on / off control allows for immeadiate ventilation; can be used with any existing bath fan Makes Any Fan Humidity Sensing Adjustable condensation sensors turn bath fan on when condensation is present and off when dry Blue LED light indicates the bath fan is on Moisture sensors prevent the growth of mold by triggering ventilation Includes adjustable condensation sensor and adjustable fan timer Manual on/off control allows for immediate ventilation; can be used with any existing bath fan