Dorgard is a simple, reliable acoustic device that holds a fire door open in any position and then automatically releases the door should a fire alarm sound. When Dorgard is holding a fire door open it listens for the continuous sound of a fire alarm. It needs to hear a fire alarm that exceeds 65dB (sound level) for longer than 14 seconds to release the door. Inexpensive to buy. Quick and easy to install. It simply screw fixes to the bottom of the door in a matter of minutes with no risk to the fire door’s integrity. The rubber plunger/stopper is in contact with the floor and, unlike conventional magnetic retainers the Dorgard can hold the door in any position. When the fire alarm is sounded, Dorgard’s integral audio electronics retracts the plunger/stopper to allow the door to close.