Fail Safe vs Fail Secure: Choosing Electrified Door Hardware

Fail safe vs fail secure describes what an electrified device does to the outside of a door when its power is cut. A fail safe product unlocks without power and needs current to stay locked. A fail secure product stays locked without power and needs current to release. In most cases the label tells you about entry from the secure side, not whether people inside can get out.

Quick answer: Choose fail secure for entrances and perimeter doors, because the door stays locked during an outage while the lock or exit device still lets occupants leave. Interior access-controlled doors depend on what your jurisdiction requires. Choose fail safe where the opening must unlock on power loss or fire alarm, such as stair re-entry doors. Fire doors using electric strikes need fail secure strikes. Mills & Nebraska can match each opening to the right electrified function.

What do fail safe and fail secure actually mean?

Both terms describe the key side, the outside or secure face of the opening, at the moment power is removed. Allegion's Decoded article on fail safe vs fail secure, written by its Manager of Codes and Resources, frames the definitions exactly that way: power is applied to lock a fail safe product and applied to unlock a fail secure one.

The egress side is a separate question. That same article notes that most electrified products allow free exit whether they are fail safe or fail secure, with electromagnetic locks as the main exception. So a power failure on a fail secure opening locks people out, not in.

Which devices can be fail safe, fail secure or both?

The answer depends on the device family, and two families have no choice at all. Detex, one of the manufacturers Mills & Nebraska carries, publishes a comparison of its electrified products showing which ones are field selectable.

• Electric strikes: offered in either mode, and the Detex table shows its own strikes and lever trim as field selectable. The lockset or exit device still controls exit.
• Electrified mortise and cylindrical locks: offered in either mode. The outside lever is powered locked or powered unlocked, and the latch stays projected until someone turns the lever.
• Electrified trim on exit devices: works like an electrified lock on the outside lever, while the pushpad or crossbar always opens the door from inside.
• Electric latch retraction exit devices: fail secure only. Power pulls the latch in, and losing power lets it project again.
• Electromagnetic locks: fail safe only, because there is no magnetic bond without current.

When you write a hardware set, name the mode next to each electrified item. A strike listed without a mode is an open question that someone will answer later, possibly wrongly.

Why do fire doors need fail secure electric strikes?

A fire door has to latch positively when it closes, and a fail safe strike gives up that latching when power goes away. The Allegion article states that electric strikes on fire-rated doors must be fail secure, because fail safe strikes do not provide the positive latching and the listings NFPA 80 requires. In the article's words, the strike must be fail secure so the door is positively latched if there is a fire.

The same source points out that fire doors require fail secure electric strikes only; an electrified lock on a fire door may be fail safe, since its latch keeps engaging whether or not the lever is powered. Confirm every component against its own listing and the fire-rated openings requirements for that assembly.

When is fail safe the right choice?

Pick fail safe when the opening must let people in from the secure side during a fire alarm or a power failure. The Allegion article identifies stair doors that provide re-entry as the classic case: the stair-side lever stays locked under power and unlocks when the fire alarm or fire command center removes power, depending on the code your jurisdiction has adopted. Occupants may then leave the stair to find another exit if necessary.

Because those stair doors are fire doors, re-entry is handled with a fail safe electrified lock or fail safe exit device trim rather than a fail safe strike. For the code details behind re-entry and egress, check the edition your jurisdiction enforces and review the Florida Building Code resource.

Accept the trade-off with your eyes open. A fail safe opening is unlocked every time the alarm sounds or the power drops, which is a real security gap on doors that do not need to admit people in an emergency.

When is fail secure the better default?

The Allegion article says fail secure products are more common than fail safe because of security concerns; an outage leaves the building closed to outsiders while exit stays mechanical. Detex lists main entrances, employee entrances and perimeter doors as common fail secure locations. The Allegion author describes specifying fail secure strikes in almost all applications, except where access upon fire alarm is required.

Power draw is a second reason. Detex notes that fail safe devices need continuous power to remain locked, while fail secure devices use power only when unlocking. Detex adds that continuous power raises energy consumption and operating costs, and Allegion notes that power consumption may also be an issue.

How do magnetic locks change the decision?

A maglock removes the choice: it is always fail safe, and it does not give free exit on its own. According to the Allegion article, a magnetic lock released by door-mounted hardware such as a request-to-exit switch in an exit device must unlock on loss of power. One released by a motion sensor must also unlock from a push button beside the door, on fire alarm or sprinkler activation, and on power loss.

If those release conditions are a poor match for the opening, one option is a fail secure strike paired with a mechanical lock or exit device, which keeps exit mechanical. Our electric strike vs maglock comparison walks through that decision in more depth.

How should you write fail safe or fail secure into a submittal?

Put the mode, the power source and the release triggers on every electrified line of the hardware set. A useful line names the device, for example a Von Duprin exit device with electrified trim or an HES electric strike, then states fail safe or fail secure, the voltage, and whether a fire alarm signal is part of the sequence. Coordinate the lock side with the frame preparation, so the strike pocket and wiring path in the hollow metal frame match the device you selected.

For specification support on these choices, an Architectural Hardware Consultant works on staff through the hardware specification service. Browse the exit devices and commercial door locks Mills & Nebraska supplies to see the families involved.

FAQs

Is a fail secure lock dangerous in a power outage?

Generally no, because the mode controls entry from outside rather than exit from inside. On a fail secure electrified lock or strike, occupants still leave by turning the inside lever or pushing the exit device. The exceptions are double cylinder institutional locks and magnetic locks, which need their own release planning.

Can an electric strike be changed from fail safe to fail secure in the field?

Some can. Detex, for example, sells electric strikes with a field selectable mode, so the installer sets the function on site. Check the specific model's instructions, and remember that a strike on a fire door has to be set and listed as fail secure regardless of what the device allows.

Are electric latch retraction exit devices fail safe?

No. Electric latch retraction is available only as fail secure, meaning the latch projects again when power is removed. That behavior lets these devices give push and pull operation during the day and still latch the door when power is cut or a fire alarm signal drops the power supply.

Which uses more power, fail safe or fail secure?

According to Detex, fail safe hardware typically uses more, since it must be energized the whole time the door is locked, which raises energy consumption and operating costs. Fail secure hardware draws current only while it is unlocking.

Contact Mills & Nebraska for help choosing the electrified hardware for each opening.