An automated garage door closing device for a remote controlled overhead garage door wherein the device is mounted on one of a pair of parallel tracks receiving rollers suitably mounted on the outer edges of the door panels, the device including a switch housing containing a switch for the leading edge of the door, and a circuit located in a second housing adjacent the garage floor and including an interval timer acting to close the door after a predetermined period of time, an audible alarm which is activated upon the garage door reaching the fully open position, a switch deactivating the entire unit when the garage door is deliberately to be left in the fully open position, and a flexible switch arm extending through the switch housing to a position to engage the upper edge of the garage door panel and acts to activate the automated closing device. A recycle delay circuit in the timing circuit acts to deactivate the unit upon interruption of the door closing operation if door movement is reversed and returned to the open position, and a sensor providing a sensor beam adjacent the garage floor to measure the time interval of interruption of the sensor beam to determine if a vehicle has exited or entered the garage or a person or animal has interrupted the beam. Also, a carbon monoxide detector is inserted in the circuit to provide activation of the door opening cycle if the level of carbon monoxide reaches a dangerous level.