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Delayed-Egress Locking Systems On Exit Doors
For safety reasons, building and fire codes require a specific number of exit doors out of every occupied portion of the building. In most cases, at least two exits out of each room is required. Many times, doors are installed specifically as "emergency exits", and are used for no other purpose. Exit doors must allow exit at all times and therefore must be kept unlocked in the direction of exit.
Unfortunately, exit doors can often create a security weakness. This is especially true when they are located in out of the way places that are unattended by employees or security personnel. For example, in a retail store, emergency exit doors are often located in the rear of the store, far away from the front check-out area. A thief can grab merchandise, and then quickly run out one of the exit doors. A similar type of vulnerability exists in many other types of commercial and institutional settings, where items of value can be taken out of the building through an emergency exit door.
To combat this problem, emergency exit doors are often equipped with "exit alarms". Exit alarms are installed on the emergency exit door, and will cause an audible alarm to sound when the exit door is opened.
Exit alarms do a good job of discouraging misuse of the emergency exit doors by employees and the general public, but don't always stop a more aggressive thief. This is because the thief knows that it will take time for an employee or a security person to respond to the door when the alarm sounds. This gives the thief ample time to grab the merchandise, and then quickly run out the door. The alarm sounds, but by the time an employee responds to the door, the thief is long gone.
In recognition of this problem, many building codes have been modified to allow the use of "delayed-egress locking systems" on emergency exit doors. The delayed egress locking system typically consists of an exit push bar, an auxiliary locking device, an audible alarm, and a special electronic control package. The delayed-egress locking system operates as follows:
The advantage of the delayed-egress locking system is that it provides a delay between the time that a person activates the alarm and when the door actually unlocks. This delay gives additional time for an employee or security person to respond to the door once the alarm has been activated. The delayed-egress locking system serves as a strong deterrent to the "grab and run" thief who doesn't want to wait 15 seconds or more to make his exit from the premises.
Most building and fire officials will approve the installation of a delayed-egress locking system provided that the following requirements are met:
There are three basic types of delayed-egress locking systems.
The first type of delayed-egress system uses an electromagnetic lock in conjunction with either a standard mechanical push bar or an electronic "touch sense" bar. These types of systems generally require an external control panel.
The second type of delayed-egress system uses an electromagnetic lock that contains a built-in control system and a built-in "exit sensor". The exit sensor detects when the door is pushed open and eliminates the need for any special type of exit push bar. This makes it ideal for retrofit installations on existing exit doors.
The third type of delayed-egress system uses a special type of mechanical exit device. All components of this system are contained within the exit device itself. This type of system minimizes the number of components required at the door and is best suited for new construction applications.
Here are a few things to consider before installing a delayed-egress locking system:
Many delayed-egress systems offer a "nuisance" alarm feature. This feature minimizes false alarms by sounding a short audible tone whenever a person first presses on the door. If the person stops pressing on the door within one second, the tone stops, and the delay sequence is not initiated. If the person presses on the door for longer than one second, then the exit alarm sounds and the 15 second countdown begins.
Some delayed-egress systems now offer a voice announcement feature. This feature gives warning messages in a human voice and can provide a verbal countdown of the time remaining until the door unlocks.
Have additional questions about the use of delayed-egress systems? Please contact us.
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