Security Glossary

REX Sensor
(Request to Exit)

A REX sensor is a device that automatically signals an access control system to release a locked door when someone approaches to leave — no card, fob, or button press required. In NYC buildings where egress compliance and smooth traffic flow both matter, getting the REX setup right is essential.

Egress Compliant Works with Mag Locks & Electric Strikes Passive Infrared or Motion Detection
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What It Is

Understanding the REX Sensor

A Request to Exit (REX) sensor is a device installed on the interior side of a controlled door that detects when someone is approaching or reaching for the door to leave. When triggered, it sends a signal to the access control panel to momentarily unlock the door — whether that door is held shut by a magnetic lock or an electric strike — so the person can exit freely without badging out or pressing a push-to-exit button.

Most REX sensors use passive infrared (PIR) technology, the same principle as a motion-activated light. The sensor monitors heat signatures in its detection zone. When it picks up the warmth of a person moving toward the door, it fires a relay signal — typically a dry contact closure — to the access control panel or directly to the locking hardware. That signal suppresses the lock for a set duration (usually 3–5 seconds), the door opens, and then the lock re-engages automatically. Some installations use a separate "push to exit" button as a backup or primary REX device, but PIR sensors are preferred in high-traffic locations because they require no physical contact.

In NYC, REX sensors are a standard component of any properly installed access control system, especially in commercial spaces, co-ops, condos, and multi-tenant office buildings. New York City building and fire codes require that all doors in a means of egress open freely from the interior — meaning an access-controlled door cannot trap occupants inside. A properly configured REX sensor satisfies this requirement by ensuring the locking device releases the moment anyone approaches from the secured side. The NYC Department of Buildings (DOB) and FDNY both pay attention to egress compliance during inspections, and a missing or improperly wired REX sensor is a common citation.

If your door sees very low exit traffic and you want a more deliberate release mechanism, a hardwired push-to-exit button is a simpler and lower-cost alternative. But for busy corridors, office suites, or any door where you don't want employees fumbling for a button with hands full, a PIR REX sensor is the better choice. Some installations use both — the PIR sensor as the primary and the button as a manual backup — which is considered best practice in high-security environments.

Key Facts

What You Should Know About REX Sensors

01

They're Required by Code

NYC fire and building codes mandate free egress from the interior of any access-controlled door. A REX sensor (or push-to-exit button) is the standard code-compliant solution. Without one, your magnetic lock or electric strike can legally trap occupants — which is a serious violation.

02

Placement Determines Performance

A REX sensor mounted too high, too far from the door, or at the wrong angle will either false-trigger (unlocking the door when no one is there) or miss the approach entirely. Standard mounting height is 7–8 feet on the interior frame or wall, angled to cover the door swing zone — something an experienced low-voltage installer gets right the first time.

03

Works with Both Lock Types

REX sensors are compatible with both magnetic locks (maglocks) and electric strikes — the two most common locking devices in NYC access control installs. The wiring configuration differs depending on whether your lock is fail-safe (maglock) or fail-secure (electric strike), so the REX must be wired correctly for your specific hardware.

04

No Badging Out Required

Unlike entry — where a credential (card, fob, PIN) is required — exit through a REX-equipped door is credential-free. This is intentional: the system logs who came in, but exit is always unobstructed. In high-security setups that require exit credentials (anti-passback environments), the REX is still present as a failsafe override.

Common Questions

FAQ: REX Sensor (Request to Exit)

Yes — any door that is electrically locked must allow free egress from the interior under NYC Building Code and FDNY regulations. A REX sensor or a hardwired push-to-exit button satisfies this requirement. Magnetic locks in particular must release immediately upon approach or contact from the inside. Skipping a REX device is not only a code violation — it's a liability issue if anyone is ever trapped during an emergency.
A PIR REX sensor is passive — it detects motion or body heat automatically and releases the lock without any physical interaction. A push-to-exit button requires the person to physically press it before the door unlocks. PIR sensors are more convenient for high-traffic doors and reduce wear on hardware. Push-to-exit buttons are simpler, lower cost, and preferred where you want a deliberate, intentional exit action — like a server room or a pharmacy back office. Many installs use both for redundancy.
False triggers are almost always a mounting or sensitivity issue. Common causes include: the sensor aimed at a heating vent or radiator (common in NYC brownstones and older buildings), the detection zone covering a busy hallway on the other side of the door, or the sensitivity dial set too high. An experienced installer can reposition the sensor, adjust the detection angle, or tune the sensitivity to eliminate false trips without sacrificing coverage.
In most cases, yes. REX sensors wire into the access control panel at the same door input where a push-to-exit button would connect — it's a standard terminal on virtually every panel brand (Lenel, Genetec, Honeywell, Avigilon, and others). If your existing system was installed without a REX device, adding one is usually straightforward as long as there's conduit access or a pathway to run wire. We assess this during a site visit before quoting any retrofit work.
The REX sensor itself requires power to operate, but egress during a power failure is handled by the lock type. Magnetic locks are fail-safe — they release when power is cut, so the door automatically unlocks during an outage regardless of the REX sensor. Electric strikes can be configured either way (fail-safe or fail-secure) depending on the application. Your installer should configure the system so that a power failure never results in occupants being trapped, which is a core requirement under NYC fire code.

Related Terms

Keep Learning

REX sensors don't exist in isolation — they're one piece of a complete access control system. These related glossary entries will help you understand the full picture.

Access Control Electric Strike vs Magnetic Lock Keypad vs Keycard vs Fob

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