How to Use REX (Request-to-Exit) Sensors with Access Control Systems

A Request-to-Exit (REX) sensor is an essential component of a professional access control system. It allows authorized personnel to exit a secured area safely while maintaining proper system integrity and compliance with fire and life-safety codes. When installed and programmed correctly, REX sensors ensure smooth operation and prevent false alarms or forced-door events.

What Is a REX Sensor?

The Request-to-Exit (REX) sensor detects motion or presence near an exit door and signals the access control system to unlock the door momentarily, allowing safe egress. REX devices are required on most fail-secure electric strike or electrified latch retraction systems where interior egress must be free and unobstructed.

• Passive infrared REX: Detects motion within a defined field near the exit door.
• Active REX button: A push-to-exit button wired in parallel for redundancy and code compliance.
• Time-based control: REX signals are programmable for adjustable unlock durations and door-held-open logic.

Why Avoid Fail-Safe Magnetic Locks

While fail-safe magnetic locks are commonly sold as “quick solutions,” they pose serious physical security and safety risks when used in the wrong applications.

• Power Failure Vulnerability: Fail-safe locks automatically release during power loss, leaving your facility unsecured.
• Fire Department Access: In many Austin-area jurisdictions, magnetic locks can block fire department entry during emergencies, violating code requirements.
• Hardware Damage & Delays: Inconsistent power or faulty REX timing can cause false releases or door-held-open alarms.
• Code Restrictions: IFC, NFPA 101, and Texas TAC 34.7 regulations often restrict or require special permits for magnetic locking hardware.

Best Practice: Use Fail-Secure Hardware

A fail-secure electrified lock (such as an electric strike or motorized crash bar) remains locked when power is lost, preserving physical security. When paired with a REX sensor and compliant fire alarm interface relay, this configuration provides the safest and most reliable access control solution.

1. Install a dedicated REX motion sensor above the interior door.
2. Add a push-to-exit button for manual release (code required).
3. Wire the door release through a fire alarm relay for automatic unlock during evacuation.
4. Program door-held-open timers and alarms through the access control software.

Local Austin Code Compliance

In Austin, Texas, and surrounding areas, access control systems must comply with NFPA 101 Life Safety Code, IFC 2015 Section 1010.2, and Texas Administrative Code 34.7. REX sensors are part of that compliance—ensuring free egress while maintaining security. Always verify installation plans with your local Fire Marshal or AHJ before using magnetic locks.