The Sensor Is Installed. The Door Still Does Not Release. Sound Familiar?
Request-to-exit (REX) sensors are a small but critical component of every electrified door opening. Mount one two inches too high, angle it toward a wall instead of the walkway, or choose the wrong sensor type for the application, and the access control system you specified or installed will fail in the field -- not because of the lock or the panel, but because of a $40 motion detector in the wrong spot.
This guide is for commercial electricians, low-voltage integrators, facility managers, and specifiers who need a clear, practical framework for REX sensor placement decisions -- from a school corridor to a hospital clean room to an industrial shipping door.
What Is a REX Sensor?
A request-to-exit (REX) sensor is a device on the secure (egress) side of an electrically controlled door that signals the access control system to release the lock so a person can exit freely. The signal interrupts power to a magnetic lock, triggers an electric strike, or commands an electrified latch -- depending on the locking hardware specified. REX devices come in two primary forms:
- PIR (passive infrared) motion sensor -- detects body heat moving through its field of view; completely hands-free egress.
- Push-button station (REX-PB) -- a surface-mounted button the user presses; simpler to wire, easier to troubleshoot, but requires deliberate action.
Both types appear on electrical drawings as [REX-PIR] or [REX-PB] and connect to the access control panel or directly in series with the lock power circuit.
PIR Sensor Mounting: The Four Variables That Control Performance
1. Mounting Height
Most PIR REX sensors are designed to be wall-mounted between 7 and 9 feet above finished floor (AFF). At that range the detection cone covers a standing adult approaching the door without triggering from hallway traffic on the other side of the door or from people standing nearby but not exiting. Mounting lower than 7 feet often causes nuisance trips from people passing parallel to the door; mounting higher than 9 feet narrows the ground-level detection footprint too much and creates a dead zone at the threshold.
Always check the specific sensor manufacturer's data sheet -- some units are rated for ceiling mount (looking straight down) and have a different height range, typically 8 to 12 feet, with a circular detection pattern.
2. Detection Angle and Aiming
PIR sensors do not detect motion in a full sphere. They have a defined detection cone, commonly described in degrees of horizontal and vertical coverage. A typical wall-mounted REX PIR may offer 90 to 120 degrees of horizontal coverage and 30 to 60 degrees of vertical spread.
- Aim the sensor toward the approach path, not the door face. Someone walking toward the door should enter the detection zone 3 to 5 feet before reaching the hardware.
- Avoid aiming directly at HVAC diffusers or radiant heat sources -- sudden temperature changes can cause false triggers on some sensor technologies.
- In healthcare corridors, where patients may move slowly in wheelchairs or on gurneys, choose a sensor with adjustable sensitivity and a wide low-angle coverage to detect slow movement reliably.
3. Masking and Sensitivity Adjustment
Many commercial PIR REX sensors include physical masking strips or DIP-switch sensitivity settings. Use masking to block detection zones that face a parallel hallway or adjacent space where foot traffic should not trigger a release. This step is frequently skipped on first install and becomes the source of most nuisance-unlock complaints after move-in.
4. Coverage Overlap at Pairs of Doors
On paired doors -- common in school cafeteria entries, hospital suite entries, and retail stockroom openings -- each leaf typically gets its own REX sensor wired to its respective lock circuit. Confirm the detection zones do not overlap in a way that releases the wrong leaf, and that each sensor's output is wired to the correct device on the access control panel.
Push-Button REX Stations: Placement Rules
Push-button exit stations are governed by a different set of concerns -- less about detection geometry and more about code and ergonomics.
- Mounting height: IBC and NFPA 101 both require the manual release device for access-controlled egress doors to be mounted between 40 and 48 inches AFF -- the same ADA reach range for controls and operable hardware.
- Distance from door: The code-required push-to-exit button must be within 5 feet (60 inches) of the door it controls and must directly interrupt lock power -- not route the signal through a CPU or time delay.
- Signage: Clearly label the button PUSH TO EXIT per code. This is not optional and is frequently flagged during fire marshal inspections.
- Lateral placement: Mount the button on the pull side of the door, not behind the swing arc. An occupant approaching to exit should be able to press the button without reaching around the door or standing in the door's path of travel.
Application Context: What Changes by Facility Type
Schools and K-12 Facilities
Vandalism risk is real. Specify vandal-resistant REX push stations with stainless steel or heavy-gauge metal faces in corridors accessible to students. PIR sensors at vestibule entries should be mounted near the ceiling where students cannot easily interfere with them.
Healthcare
Infection control matters. Hands-free PIR egress is preferred in clinical spaces so staff do not need to touch a button while gloved. Confirm the sensor sensitivity handles slow movement from patients in wheelchairs or on IV poles. In clean rooms and sterile processing, check whether the sensor housing material and finish are compatible with cleaning agents used in the space.
Industrial and Warehouse
Forklift-accessible areas need sensors mounted high enough to avoid vehicle damage and aimed to detect pedestrians -- not moving equipment. Consider ceiling-mount PIR units in areas where wall space near the door is occupied by shelving, dock equipment, or machinery.
REX Sensor Wiring: The Detail That Breaks Most Installs
A PIR REX sensor in a typical single-door maglock circuit is wired in the power path to the lock -- when the sensor detects motion, it opens its relay output, cutting power to the lock so it releases. Some systems wire REX to a panel input instead; verify the wiring topology against the project drawing before terminating.
For access-controlled egress doors, the push-button station must directly interrupt lock power with a minimum 30-second unlock time upon activation -- this is a code requirement under both IBC and NFPA 101, not a preference. Wiring it through a panel controller that adds processing delay can fail a fire marshal inspection.
Reference the electrical drawing legend: the REX-PIR tag and REX-PB tag should both appear on the drawing with their fail mode annotated. A sensor that holds the lock released on power loss is a fail-safe design; confirm that matches the project's intent before wiring.
Products to Consider for Your REX Application
DoorwaysPlus carries a range of request-to-exit components suited to every access control topology -- PIR ceiling and wall mount sensors, push-button exit stations in commercial and vandal-resistant grades, and complete one-door kit packages that bundle a maglock, REX station, keypad, and power supply for straightforward single-door installs. Whether you are speccing a new build or troubleshooting an existing opening, the right REX sensor placement and product selection saves time on the commissioning call and prevents callbacks after turnover.
Have questions about your specific opening? Contact the team at DoorwaysPlus.com for application guidance and product recommendations.