The battery operated Dorgard is designed to safely and legally hold open a fire door and automatically release the fire door when a fire alarm sounds. It takes approximately 5 minutes to install by fixing to a fire door with four screws. Dorgard can be used to hold a fire door open 24hours a day. However, it is recommended that fire doors are closed at night so Dorgard can be set to release at a pre-set time. When Dorgard is used to hold open a fire door, after approximately 14 seconds of the continuous sound of a fire alarm over 65 decibels, it will release, allowing the door to close under pressure from the overhead door closure.