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News & Research
September October 2014
Author(s): Ron Cote. Published on September 3, 2014.
THE ANCIENT CITY OF ATHENS used the agora, or outdoor square, as its civic center and marketplace, while the city’s fortified walls kept its enemies and other threats away. Today, civic and governmental activities take place inside buildings. The structure’s walls help to provide the environmental envelope needed for comfortable and effective function.
Door openings in exterior walls allow for ingress and egress but introduce security challenges. Building operators work to provide the systems and procedures necessary for limiting admission to those who legitimately belong, and to do so without unreasonably inconveniencing those persons. Enemies need to be denied entrance, but the task is complicated by the inability to recognize who the enemy is without time-consuming screening. Systems that control ingress must not adversely affect the safe egress of building occupants as required by
NFPA 101®, Life Safety Code®
The 2015 edition of NFPA 101, available this fall, includes provisions for security access turnstiles. The turnstiles are positioned in a building lobby, for example, to prevent unauthorized access to the occupied areas of the floor. Persons with proper credentials, typically in the form of electronic cards, signal the turnstile panels to retract, allowing passage. Additional required features work together to assure that the turnstile openings can be reliably used for egress travel without occupants having to provide credentials.
NFPA 101 regulates egress in significant ways but does not require ingress. All building doors could be locked from the outside and the building could be made code-compliant. Yet, traditional locks that are locked from the outside are also locked from the inside. NFPA 101 permits the use of three specialized forms of door locking hardware that allow for safe egress while denying access to unauthorized persons:
Electrically controlled egress door assemblies. The door is held in its locked position by an electromagnet. Entry from the exterior, if it is to be permitted, is typically gained by a card reader. The door can be opened from the interior via a lock/latch release, installed on the door leaf, that directly removes power from the electromagnet. The occupant sees the unlocking process as being no different than that performed for a mechanically released latch, but the locking and unlocking mechanisms are electronic.
Access-controlled egress door assemblies. The door is held in its locked position by an electromagnet. Entry from the exterior, if it is to be permitted, is typically gained by a card reader. The door can be opened from the interior by pushing on the door leaf as a motion detector senses an approaching occupant and electrically unlocks the door. Should the unlocking mechanism fail, a PUSH TO EXIT button, located to the side of the door opening, overrides the lock so as to provide a redundant unlocking means. Additional required building system and hardware features work together to assure that the access-controlled egress door assembly does not compromise life safety.
Delayed-egress locking systems. The door is locked from the exterior and interior, typically by an electric strike. An interior push pad initiates the unlocking process. As the hardware name implies, there is a delay before the door can be opened. After 15 seconds, the push pad is again depressed so as to open the door. Additional required building system and hardware features work together to assure that the delayed-egress locking system does not compromise life safety.
The above examples show that security can be provided in concert with NFPA 101 compliance. In a future column we’ll explore the door locking permitted in health care occupancies where the clinical needs of patients require specialized security measures for their own safety or where patients pose a security threat.
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