Fail safe vs. fail secure: When and where to specify

All images courtesy Allegion
All images courtesy Allegion

by Lori Greene, AHC/CDC, CCPR, FDAI, FDHI
Many specifiers are uncertain of the difference between fail-safe and fail-secure security products, and how these functions apply to electric strikes, electromechanical locks, panic hardware, and electromagnetic locks. The two terms have both life safety and security implications.

While fail-safe products are unlocked when power is removed (i.e. power is applied to lock the door), fail-secure products are locked when power is removed (i.e. power is applied to unlock the door). Fail safe/fail secure refers to the status of the secure side (key side, outside) of the door. Most products provide free egress whether they are fail safe or fail secure.

Electric strikes
An electric strike replaces the regular strike for a lockset or panic hardware to electrically control access. For a single door, the electric strike mounts in the frame, and for a pair, it mounts in the inactive leaf or on a mullion. The lockset or panic hardware still functions as it normally would—free egress is available at all times, except in the case of double-cylinder institutional function locks.

The spring-loaded keeper on the electric strike controls the latchbolt of the lock or panic hardware. When access is allowed, the keeper is free and the latchbolt can be pulled through the keeper, so the door can be opened. When the strike is secure, the keeper secures the latchbolt and prevents the door from being opened. In most cases, a key can be used to retract the latchbolt from the secure side of the door to allow access if a manual override is needed. Since the lock or panic hardware functions independently of the electric strike, you can exit by turning the lever or pushing the touchpad of the panic hardware, regardless of whether the electric strike is fail safe or fail secure.

For electric strikes on fire-rated doors, fail-secure strikes must be used per the National Fire Protection Association (NFPA) 80, Standard for Fire Doors and Other Opening Protectives. Fail-secure strikes are typical for most applications, except when access is required upon fire alarm. There are very limited situations where access upon fire alarm is required. It is also important to know the use of an electric strike does not affect firefighter access. Their method for access on a door with a mechanical lockset (e.g. key or access-control credential in the key box or a tool) can still be used.

Additionally, there are security concerns with fail-safe hardware. Should the building or area be unlocked and free access be provided every time there is a power failure? A breach of security can be extremely dangerous for building occupants, along with the potential for loss or damage.

Electromechanical locks
An electromechanical lock is a lockset which has been electrified so it can be controlled by a card reader, remote release, or other access control device. Most electromechanical locksets allow free egress at all times. There are double-cylinder electromechanical locksets which do not allow free egress, just like a double-cylinder mechanical lockset, but neither of those should be used on doors required for egress. Note a lock with two key-cylinders may be a classroom security lock, which allows free egress, and not an institutional function lock, which does not allow free egress.

A fail-secure electromechanical lockset is locked on the secure side when there is no power to the lock. To unlock it, power is applied and the lever can then be turned to retract the latch. The latch remains projected until the lever is turned.

A fail-safe electromechanical lockset is locked when power is applied. When power is removed, the lever can be turned to retract the latch. Fail-safe electromechanical locks are used for stairwell doors providing re-entry. The lock is constantly powered so the lever on the stair side is locked. During a fire alarm, the lever on the stair side is unlocked (power removed) either by the fire alarm or a signal from the fire command center, depending on which code has been adopted. Building occupants may then leave the stair to find another exit if necessary. The stair doors would also be unlocked during a power failure. The locks always allow free egress into the stair, with the exception of the stair discharge door, which can be mechanically or electrically locked on the outside but allows egress out of the stairwell.

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