Panasonic FV-08VKS2 WhisperGreen 80 CFM Premium Ceiling Mounted Continuous and Spot Ventilation Fan Incorporates a totally enclosed DC motor designed for extremely quiet, energy-efficient operation SmartFlow Optimum CFM Technology automatically increases the fan's speed to ensure that the desired CFM is actually achieved CustomVent Variable Speed Control allows the fan to run continuously at a pre-set lower level of 0-70 CFM High/Low delay timer will return fan to minimum CFM level after period of time set Can be elevated to a maximum of 80 CFM when the switch is turned on