UFC 4-021-02NF
27 September 2006
change 1, 23 October 2006
hardware. Life safety codes in the United States dictate that personnel can not be
locked in such that they are restricted from free exit. When an opening is locked from
the public side and free exit is required from the secure side, there are several methods
that can be employed as discussed below. Refer to Chapter 9 for more information.
3-3.6.1 The simplest door hardware is a "crash bar". This strictly mechanical device
merely requires exiting personnel to hit the "push-to-unlock" bar. If an electric strike is
used as a door lock, generally the door has a twist door-knob handle that allows free
exit.
3-3.6.2 If magnetic locks are used to secure the door than both an automatic and
manual method of existing the door must be provided. Generally, the manual method is
a Request to Exit button, sometimes abbreviated as a REX. When this device is
pressed, power to the door locks is shunting allowing exit. The most common form of
an automatic sensing device that will release the door lock when a person approaches a
door in the exiting direction is a Passive Infrared Sensor (PIR). This device senses the
infrared heat signature of a person and automatically shunts door lock power allowing
free exit. PIRs have a significant security shortfall in that any person passing by or
loitering in the sensing area of a the opening can activate the PIR and shunt door lock
power. For this reason, magnetic locks should be the designer's last choice for door
locking mechanisms.
3-3.6.3 Card readers or keypads can be used for anti-passback, "badge out"
procedures but require building code variance or approved special circumstances for
locking an exit portal for a normal existing individual. Badge out card readers over more
specific identification of existing personnel over keypads, where a number of individuals
could have knowledge of the exit numerical code.
Table 3-1 Exit Technologies (Pros and Cons)
Pros
Cons
Easy to implement
Does not "track" who left the facility or
Door
space.
Hardware
Cost effective
No additional security.
Simple
Slightly simpler to
Generally requires complementary
Request-to-
implement than keypads or
automatic exiting devices such as a
Exit Button
cardreaders.
PIR.
No additional Pros, typically
No additional security.
mandated in U.S. by use of
PIRs can release the door lock if
"mag locks" as door locking
someone lingers in detection cone.
device.
Some additional security
Requires variance or alternate method
Keypads
afforded in that exiting
to U.S. life safety code for exit doors.
person needs to know the
Exit code can be shared.
exit code.
Additional construction cost.
30
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