The battery-powered control unit can turn the fan on or off and speed it up or slow it down from a range of 40 feet indoors (or up to 450 out of doors in the open air). An optional AC adapter allows the control unit to be powered from a standard wall outlet.   With the addition of an optional temperature sensor, the fan will start automatically when a fire is lit, and stop when the fire has gone out. It will also draw at full speed when a fire is started and slow down once ignition is established. If the fire starts to burn out, an alarm will sound indicating that more fuel is needed. An alarm will also sound if the chimney becomes too hot to warn of a possible chimney fire.   Control panel requires two "C" batteries; power unit requires 120VAC.