Electromagnetic Locks: How Maglocks Hold, What the Standard Tests, and How Egress Is Kept

The Standard: ANSI/BHMA A156.23

ANSI/BHMA A156.23 is the BHMA standard for electromagnetic locks. It sets cyclical, dynamic, operational, strength, and finish tests. BHMA's summary also states that the product "is used for access control."

Edition note: BHMA's Hardware Highlight page is headed "A156.23 – 2022," but its text refers to "A156.23-2017." This article doesn't name an edition for the figures below until the current edition is confirmed (decision X-13).

Key points from BHMA's summary:

• Durability. Grade 1 electromagnetic locks must withstand one million cycles of opening and closing and still meet the electrical and strength requirements.
• Holding force. Holding force and impact resistance are among the strength tests. Products are rated in increments, and holding force "starts at 500 pounds, and continues through 2000 and beyond."
• Electrical tests. There are five:
• residual magnetism
• over voltage
• inductive kickback
• dielectric voltage withstand
• temperature rise

Residual magnetism is magnetic hold that remains after power is removed. It matters for a lock whose whole job on egress is to let go. BHMA's summary lists the test but does not give its pass criteria.

A holding-force rating is a laboratory figure for a straight pull between magnet and armature. It is one of several tests, not a complete measure of how a door will resist force. See ANSI/BHMA lock grades.

Mounting Types

A156.23 numbers the lock types. BHMA's summary describes two examples:

• Shear lock. "Mortised in header. Armature recessed in top of door. For out swinging doors." The lock and armature are "in shear (parallel) contact when locked." Since both parts are hidden in the head of the opening, a shear lock is less visible.
• Surface-mounted lock. The lock is "mounted on face of header," with the armature "mounted on pull side of door with an angle bracket."

The full type list is in the standard. What matters most when picking a type is:

• the door's swing
• the frame and header
• how the armature can be mounted

Fail-Safe by Nature

A technical bulletin from the National Institutes of Health's Office of Research Facilities defines the two power-loss behaviors of electronic locks:

• Fail safe: when no power is applied, the door is unlocked.
• Fail secure: when no power is applied, the door is locked.

The same bulletin notes that electromagnetic locks "are typically fail safe, requiring a release device to allow for egress." It gives as examples:

• a request-to-exit switch in panic hardware
• a pushbutton actuator and sensor combination
• a fire alarm or sprinkler system trigger

By contrast, electric strikes and electrified locksets can be ordered either way. The bulletin notes that electric latch retraction on exit devices is fail secure. See electric strikes, electrified locksets, and electric latch retraction.

Egress: How Codes Keep the Door Openable

An electromagnetic lock has no lever or bar of its own, so the means of release has to be designed into the opening. Requirements depend on the code adopted locally, and the authority having jurisdiction (AHJ) has the final say. As one example, the 2021 International Building Code as adopted in Illinois (via UpCodes) includes two release arrangements. Neither section is permitted in Group H occupancies.

Sensor release (section 1010.2.12). This section requires:

• A sensor on the egress side that detects an approaching occupant and unlocks the door.
• Locks that unlock on a signal from the sensor, on loss of power to the sensor, or on loss of power to the lock.
• A manual unlocking device mounted 40 to 48 inches above the floor, within 5 feet of the door, marked "PUSH TO EXIT." It must directly cut power to the lock, independent of other electronics, and keep the lock unlocked for at least 30 seconds.
• Automatic unlocking when the fire alarm, sprinkler, or fire detection system activates, where those systems are provided.
• Emergency lighting on the egress side.
• Locking system units listed to UL 294.

Door hardware release (section 1010.2.11). Here the hardware on the door leaf itself releases the lock. It must:

• have an obvious method of operation under all lighting conditions
• work with one hand
• directly interrupt power to the lock and unlock the door immediately

Loss of power must also unlock the door. Where panic or fire exit hardware is required, operating it must release the electric lock too. Locking system units again must be listed to UL 294.

These summaries are not a substitute for the code text. Other sections, such as delayed egress, have their own conditions. See request-to-exit, panic hardware, and delayed-egress locks.

Fire Doors

According to BHMA, electromagnetic locks used on labeled fire door assemblies "shall be listed or labeled for fire doors by a nationally recognized independent testing laboratory and be subject to a periodic in-plant follow-up inspection service." Fire door assemblies also have their own latching requirements, covered in fire-rated door hardware.

Power Supplies

A maglock is only as reliable as its power. ANSI/BHMA A156.35-2025 sets performance requirements for power supplies designed for electronic access control hardware. Power supplies certified under it must meet one or more of:

• UL 294 (access control system units)
• UL 603 (power supplies for burglar alarm systems)
• UL 2610 (commercial premises security alarm units)

They also receive an energy efficiency rating.

Battery backup, fire alarm interface, and other features are system design decisions. They should match the egress arrangement the code and AHJ require for that opening. The NIH bulletin puts it plainly: for electronically locked doors, "it is necessary to coordinate with the appropriate Authorities Having Jurisdiction."

Related Topics

• Request-to-exit: sensors and switches that release the lock
• Access control and card readers: the system around the lock
• Electric strikes: the common fail-secure alternative
• Electric latch retraction and electrified locksets
• Panic hardware: required hardware in some occupancies
• Delayed-egress locks
• Fire-rated door hardware
• Magnetic keyed locks: mechanical locks with magnet-coded keys, not the same as a maglock

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