against the padlocked exit doors. Even after a police officer broke a padlock, the inward-opening doors were held shut by the mass of bodies behind them. Justification for use By the end of the 20th century, most countries had 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 crushes. 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. Such a human crush, which has many historical precedents, can cause falls, crushing, and other injury because the rear of a crowd has no idea that the people at the front of a crowd have come across a door. Crash bars are typically found on doors which are required emergency exits serving a particular type or quantity of occupants. Common locations include doors which provide egress from assembly areas, doors which serve many occupants, or doors serving hazardous areas. For buildings subject to the International Building Code, or a locally adopted variation, they are required for certain healthcare, education, or assembly spaces, generally related to the number of occupants exiting through a given door. Latching Mechanical types Crash bars offer numerous configurations for latching to the door frame. Vertical rods can be affixed to crash bars allowing both doors to be opened with no center clearance obstruction. When the bar is depressed, a chord within the vertical rod gets pulled, which lowers a latch at the top and/or bottom and allows the door to open. The Pullman latch, which attaches to a Pullman keeper, is the locking mechanism usually used at the ends of the vertical rods. More expensive products may feature vertical rods and latches concealed within the door. Some jurisdictions permit doors to latch to each other. For security, additional latching points may be added. For example, upper and lower vertical rods added to one door and connected to the leaf with no rods via a mortice latch. A double door coordinator is used to ensure the active leaf does not