Quick Code Q&A

Quick Code Q&A: Electromagnetic Locks Released by a Sensor

Continuing our conversation around electrified hardware, this post will focus on electromagnetic locks, also called mag-locks. This hardware is common due to the ease of installation, especially in retrofit applications. However, there can be confusion about the codes governing the use of electrified locking systems.

Mag-locks are common due to the ease of installation, especially in retrofit applications.

Electromagnetic locks are allowed by the I-Codes in access control systems in occupancies other than Group H – High Hazard. This hardware has two main components: the electromagnet in the housing attached to the frame and a steel armature secured to the door.  When energized, the magnet bonds to the armature and locks the door. Electromagnetic locks are typically de-energized by either a sensor release or a switch within the door-mounted hardware—both applications are required to allow free egress upon power failure. Further, model codes also require some components of these systems to be listed to UL 294 – Standard for Access Control System Units.

Separate sections included in the model codes detail requirements for each of the two application types. Only one set of requirements must be followed, depending on the method used for releasing the lock. These requirements vary by location, so verifying which model codes and editions have been adopted in a particular jurisdiction is important. The following will focus on the 2024 edition of the International Building Code (IBC), which no longer allows sensor-release mag-locks on doors required to have panic hardware. For these applications, the locks are required to be released by a switch in the panic hardware.

Question: What codes apply to doors with electromagnetic locks released by a sensor?

When an electromagnetic lock is released by a sensor that detects an approaching occupant and de-energizes the lock, the sensor must be installed on the egress side of the door, typically located above the door.

Sensor-release locks must also be unlocked for egress by an auxiliary switch that is readily available, mounted within five feet of the door and between 40 and 48 inches above the floor. These switches (typically push buttons) must allow free egress for 30 seconds or more, independent of the access control system, and must be accompanied by signage that reads “PUSH TO EXIT.”

Electromagnetic locks released by a sensor must also unlock upon activation of a fire alarm or automatic sprinkler system (if present)—the door must remain unlocked until the system is reset. A loss of power to the sensor or the lock/locking system must also result in the system allowing free egress.

The model building codes and fire codes do not define exactly what “loss of power” means nor specifically address whether battery backup is acceptable for electromagnetic locks released by a sensor. One interpretation is that the stand-by power of an electromagnetic lock is permissible if the same backup power source powers the fire alarm system.

Next month’s Quick Code Q+A will look at electromagnetic locks released by a switch inside the door-mounted hardware. Until then, for more information, see this video that details the requirements for both applications.

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