US Patent 6920874 Intelligent ventilating safety range hood

An improved ventilating range hood that drives a variable speed fan according to the state of four distinct air quality sensors: temperature, humidity, Carbon monoxide and smoke. A micro-controller is used to integrate the four signals and determine the appropriate ventilation requirement. This value is converted into a signal to drive the fan. Visual indicators are provided to display the state of each air quality factor. An audible alarm is activated if the levels remain at hazardous levels for more than a predetermined time interval after the fan has been turned on.