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Fail safe vs. fail secure: Why you should know the difference

Fail safe vs. fail secure: Why you should know the difference
Fail safe and fail secure are important concepts to know, since installing the right product can help save lives and keep company assets secure. This note discusses what their main differences are and how to make the right selection.
Fail safe and fail secure are common terms in access control and are important concepts to know and understand in order help keep people and assets safe and secure. This note discusses what their main differences are and how to make the right selection. 

What’s different between fail safe and fail secure?

Both fail safe and fail secure refer to the type of access control in the event of power outage. 
In a fail safe configuration, the door is unlocked when power is gone. “Fail safe, or fail open, requires an electric current to hold it closed. A maglock is an example of this type of lock. If there is a power failure, all the doors are unlocked. This is ‘safer’ in a fire,” said Bob Mesnik, President of Kintronics.

Fail secure, on the other hand, keeps things secure during a power failure. In fail secure mode, the door is locked when power is gone. “Fail secure is also called fail-locked or non-fail safe. In this configuration, applying an electrical current to the strike will cause it to open. If power is lost, the lock stays shut. If the door has a strike in the fail-secure configuration and there is a power failure, people can still exit by turning the knob from the inside, but the people can’t get in. A maglock would require a backup battery to be configured in a fail-secure configuration,” Mesnik said.

Electromagnetic locks originated in the 1970’s to achieve real fail-safe electric locking device. EM Locks use magnetic force and thus do not require a mechanical latch bolt to lock the door.

Fail Safe and Fail Secure both permit egress

Egress means exit. Chapter 10 of the International Building Code discusses the requirements from power operated doors as means of egress. Fail safe or fail secure refers to the status of the outside (key side) of the door.
“Doors that have fail-secure locks can also be equipped with exit devices that facilitate exit in a fire. For example, a door can include a REX (request to exit) button, a motion detector, a crash bar, or a power control from the fire alarm box that assures the door is easily opened in an emergency,” Mesnik said.

Since Electromagnetic locks require a constant supply of electricity to remain locked, they are natively fail safe. When you remove power, the electromagnetic lock unlocks. Because EM locks do not provide free egress like other electrified hardware, release devices must be installed in order to allow egress

Which one is more expensive or harder to install

When using a strike, there is usually no difference in cost or installation. Electric strike locks are electromechanical, the lock’s strike is controlled electronically to trigger the strike plate and release the lock bolt or latch. Electric strike locks can be either fail-safe or fail secure and hence allow for a wider variety of uses.

“Most strikes have two modes that are selected by the wiring. Mag-locks would require an extra battery to provide power during a power failure so they are more expensive and more complicated to wire,” Mesnik said.

Power consumption is another factor. For example, fail safe requires constant power to keep doors shut and therefore may be more expensive.

How to know if I should use fail safe or fail secure lock?

Fail safe doors are unlocked when power goes out. This ensures that first responders can get into the building quickly and freely. As such, fail safe is typically deployed in lobbies and stairwells.

Fail secure doors are locked when power goes out. This can be applied to certain areas in the building where access should still be limited even during a power outage. “There may be a reason to use fail secure in internal doors. For example, you may want to keep the computer room secure during a power failure,” Mesnik said.

Fail secure locks are also used for fire doors and stairwell doors. The reason is that in case of fire, these doors are designed to seal off that part of the building, to slow the spread of fire, and hence should remain closed.

Sometimes, both configurations are needed in the same building. According to this blogpost by Automated Systems Design, the following can be used to guide the decision on whether fail safe or fail secure should be used:

  • During a power outage, would the locked door endanger lives? If yes, use fail-safe.
  • During a power outage, would the unlocked door put valuables or sensitive information at risk? If yes, use fail-secure.

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