A panic bar, also known as a crash bar, is a device for unlocking a door and exiting quickly during an emergency situation. The mechanism consists of a spring-loaded metal bar fixed to the inside of an outward-opening door. When the lever of the panic bar is either pushed or depressed, it activates a mechanism which unlatches the door allowing those inside to leave quickly from the building.
Allowing the user to push on the door, rather than twist a doorknob or pull up or down on a lever, allows for easier and faster access. A panic bar's fast-acting mechanism causes a reduction in the risk that a rushing crowd might suddenly create a logjam at the exits. This situation can cause falls, crushing and injury because the rear of a crowd has no idea that the people at the front of a crowd have come across a door thus causing a stampede.
Many countries have laws requiring panic bars on doors for safety reasons in public buildings.