A crash bar (also known as a panic bar, exit device, panic device, or a push bar) is a form of lever tumbler lock for unlocking a door during emergency conditions. The mechanism consists of a spring-loaded metal bar fixed horizontally to the inside of an outward-opening door. When the lever is either pushed or depressed, it activates a mechanism which unlatches the door allowing occupants to leave quickly from the building.
Following the events of the Victoria Hall disaster in Sunderland, England in 1883 in which more than 180 children died because a door had been bolted at the bottom of a stairwell, the British government began legal moves to enforce minimum standards for building safety. This slowly led to the legal requirement that venues must have a minimum numbers of outward opening doors as well as locks which could be opened from the inside.
However these moves were not globally copied. For example in the United States, 602 people died in the Iroquois Theater Fire in Chicago in December 1903 because iron gates blocked exits, and at the Italian Hall Disaster in Calumet, Michigan on Christmas Eve 1913 (popularized by Woody Guthrie's song, "1913 Massacre"), 73 people (59 were children) were killed in a stampede because the entrance doors only opened inwards.
Implementation & usage 
By the end of the 20th century, most countries have building codes (or regulations) which require all public buildings have a minimum number of fire and emergency exits. Crash bars are fitted to these types of doors because they are proven to save lives in the event of human stampedes. Panic can often occur during mass building evacuations caused by fires or explosions.
In the event emergency exits are required, the crash bar works efficiently to allow people to pass through security doors without a reduction in speed. A crash bar's fast-acting mechanism reduces the risk that a rushing crowd might suddenly become a logjam at the exits. This situation, which has many historical precedents, 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.
All doors which are intended to function as emergency exit doors must have crash bars. For security reasons, most cannot be opened from the outside. However a door handle can be mounted on the opposite side to create a two-way door. This allows the bar to be locked in a neutral (latch open) position, allowing the door to be freely opened from either side.
Legal standards 
- United Kingdom
In the UK, British Standards EN179 and EN1125 apply to panic hardware for workplace access and public access buildings respectively.
- United States
Panic hardware is often required by federal OSHA (Occupational Safety and Health Administration), and municipal code in the United States for situations involving means of egress for those entities complying with the National Fire Protection Association's (NFPA 101) Life Safety Code, as well as with the National Electrical Code (NFPA 70) requirements. Additionally, some municipalities require this hardware when an occupancy is considered 'hazardous', as in the case of chemical storage facilities.
- American National Standards Institute, ANSI/BHMA A156.3-2001, American National Standard for Exit Devices
- California Code of Regulations, Title 24, Part 2, "California Building Code." 1008.1.9
- British Standards relating to Panic Hardware
- United Kingdom
- United States
- OCCUPATIONAL SAFETY AND HEALTH STANDARDS, 29 cfr 1910.36
- National Fire Protection Association 101, Life Safety Code, 2012;
- 2011 NATIONAL ELECTRICAL CODE (NEC)