Exit device applications

An emergency exit in a structure is a special exit for emergencies such as a fire: the combined use of regular and special exits allows for faster evacuation, while it also provides an alternative if the route to the regular exit is blocked by fire, etc. It is usually a strategically located (e.g. in a stairwell, hallway, or other likely place) outward opening door with a crash bar on it and with exit signs leading to it. The name is an obvious reference to when they are frequently used, however a fire exit can also be a main doorway in or out. A fire escape is a special kind of emergency exit, mounted to the outside of a building. Local building codes will often dictate the number of fire exits required for a building of a given size. This may include specifying the number of stairs. For any building bigger than a private house, modern codes invariably specify at least two sets of stairs. Furthermore the stairs are completely separate from each other. Some architects meet this requirement by housing two stairs in a "double helix" configuration where two stairs occupy the same floor space, intertwined. It may make no functional sense to have two stairs so close to each other, but it meets the requirements of the building codes. Knowing where the emergency exits are in buildings you frequent can save your life. Some buildings, such as schools, have fire drills to practice using emergency exits. Many disasters could have been prevented if people had known where fire escapes were, and if emergency exits had not been blocked. For example, in the September 11, 2001 attacks on the World Trade Center, some of the emergency exits inside the building were inaccessible, while others were locked. In the Stardust Disaster and the 2006 Moscow hospital fire the emergency exits were locked and most windows barred shut. The Station Nightclub was over capacity that night, the front exit was not designed well (right outside the door, the concrete approach splits 90 degrees and a railing runs along the edge, and an emergency exit swung inward, not outward as code requires. In aircraft terms, an "exit" is any one of the main doors (entry doors on the left side of the aircraft and service doors on the right side) and an "emergency exit" is defined as a door that is only ever used in an emergency (such as over wing exits and permanently armed exits). The number and type of exits on an aircraft is regulated through strict rules within the industry and is based on whether the aircraft is single or twin-aisled, the maximum passenger load and the maximum distance from a seat to an exit. The result (via model and practical testing) is that a commercial jet will be able to evacuate it's designed maximum occupancy of passengers within 90 seconds through only half of the available exits.