Request to Exit (REX): Sensors, Switches, and Free Egress

Two Jobs for One Signal

Monitoring. Access control systems watch for a door opening without a valid credential. A REX input tells the system that the door was opened from the inside by someone leaving, not forced. Lori Greene of Allegion notes on I Dig Hardware that "some sensors mounted above the door are used by the security system to signal that someone has exited and may not be related to the locking or unlocking of the door."

Releasing the lock. On some electrified doors, the REX device is what unlocks the door for egress. I Dig Hardware describes systems that "use an electronic switch in the lever handle, panic hardware, or electronic touch-sensor bar to release the mag-lock for egress," and notes that "this switch is often called a request-to-exit switch or RX/REX switch."

Which job a REX device performs decides which code rules apply.

Types of REX Device

• Switches in door hardware. Many electrified locks and exit devices can carry a built-in switch that changes state when the inside lever or push bar is operated. Schlage's ND Series electrified cylindrical lock, for example, offers a Request to Exit (RX) option that can be "easily upgraded in the field," with normally open and normally closed contacts for wiring to a controller.
• Sensors above the door. A sensor on the egress side detects a person approaching the door.
• Push buttons. A wall-mounted button, often labeled "PUSH TO EXIT," that releases an electric lock. In the sensor-release arrangement described below, the model codes call for this as a separate manual release.

When REX Is Only a Signal

Most access-controlled doors do not depend on REX for egress. The 2021 IBC Commentary, quoted on I Dig Hardware, says that "the most common application for electrified hardware is one where an access control reader on the ingress side of the door controls access, and the door hardware on the egress side allows free egress at all times." Such a door is treated like a door with an ordinary mechanical lock.

A typical example is an electrified lever lock or an exit device with electric latch retraction. The inside lever or push bar opens the door mechanically, so any REX switch on it is only reporting.

When REX Releases the Lock

Doors held by electromagnetic locks have no mechanical latch for occupants to release. Power must be cut to the magnet. The model codes address two arrangements, as summarized by I Dig Hardware:

• Sensor release. A sensor on the egress side detects an approaching occupant and unlocks the lock. The 2024 IBC language quoted in an I Dig Hardware training presentation also requires that loss of power unlocks the lock and that a separate manual unlocking device near the door releases the lock independently of other electronics.
• Door hardware release. A switch in the door-mounted hardware releases the lock. The quoted 2024 IBC language requires that operating the hardware "directly interrupts the power to the electric lock and unlocks the door immediately," that it can be operated with one hand, and that it has an obvious method of operation under all lighting conditions.

The same I Dig Hardware material notes that in the 2024 IBC, locks used in these sensor-release and door-hardware-release systems need a UL 294 or UL 1034 listing.

Section numbers, mounting heights, timing, and fire alarm interfaces change between code editions and between the IBC and NFPA 101. They also vary by jurisdiction, so this article does not restate them. Check the adopted code with the AHJ.

A Common Misreading

Lori Greene notes that older model codes titled the sensor section "Access Controlled Egress Doors," "leading some to believe that this section was applicable to every door equipped with an access control reader." The titles were changed to show that the sections apply only to locks released by a sensor. The 2024 IBC also adds wording that access-controlled doors may simply be "readily openable from the egress side without the use of a key or special knowledge or effort."

REX and Fail-Safe Locks

REX release is usually discussed together with fail-safe locks, the kind that unlock when power is removed. An NIH technical bulletin notes that electromagnetic locks "are typically fail safe, requiring a release device to allow for egress (e.g. a sensor combination, or fire alarm/sprinkler system trigger)." See electrified locksets for fail-safe and fail-secure locks with mechanical egress.

Related Topics

• Electromagnetic locks: holding force and release
• Access control: readers, controllers, and door position
• Card readers
• Electric strikes
• Panic hardware
• Electric latch retraction
• Delayed egress locks

Sources

Note: the code content rests on one expert publisher (I Dig Hardware) quoting the IBC and its Commentary, not on the ICC text itself.