A panic bar on a door works by pushing on the device, that causes a latch mechanism to retract. A panic bar, which is also referred to as a crash bar, is a device found on the inside of a door in buildings, such as school, hospitals and hotels.
A panic bar device can consist of components that include a metal bar with a spring-loaded mechanism, lever and latching mechanism. By depressing the lever that is attached to the bar, the latching mechanism is released and the door opens. This allows people to exit a building through this door during an emergency, such as a fire.
There are different types of panic bars, including rim, surface vertical rod and concealed vertical rod. Some features found on some panic bars are an alarm and delayed egress. Fire rated door exits need these devices and are regulated by states building codes or the National Fire Protection Association.