Fail Safe and Fail Secure Locks

IImage by Nenad Maric from Pixabay

Fail-secure and fail-safe - two words that one probably comes across in electric door brochures. What are they, and how do they make a difference? How to make a choice? Let's find out. 

Fail-safe doors get unlocked when power is removed, i.e., power is required to keep these doors locked. On the other hand, fail-secure doors are locked when the power is removed. In this case, power is needed to unlock the door. 

In both these locks, leaving the building in case of an emergency (egress) is not affected in any way. These types of locks only control 'ENTRY' and the terms safe and secure only refer to the status of the secure side. 

In fail-safe locks, the door is unlocked by default. However, power is applied during business hours to keep the door locked. It is called 'fail-safe' since the door automatically unlocks during a power failure, thus allowing people to escape in an emergency. If you plan to use Magnetic locks (maglocks), this is the kind of lock you're looking at. The magnet works as long as there is a current, and when the current is switched off, it stops working. 

Fail secure locks are the exact opposite. They stay locked even if the power supply is interrupted. That's why they're called 'fail-secure.' It is locked by default and so secure. They can be seen in huge bank vaults and other high security, entry-restricted areas. 

 There are four standard electric locks - 

• Electric strikes

• Electromechanical locks

• Electromagnetic locks

• Electrified exit devices.

Each of these comes in both fail-safe and fail-secure models. Now, let's look at where to use which type of lock - fail safe or fail secure. 

Electric strike doors with fail-secure locks are used in fire-rated doors. Fail-safe strike doors do not provide positive latching and other standards for fire doors. Instead, they remain locked at all times, thus preventing the spread of fire.  Fail secure strikes can also be unlocked using mechanical keys for firefighter access. 

Fail-safe strike doors can be used in non-fire-rated doors that must remain unlocked in emergencies other than fire. 

 Electromechanical or Electrified Mortise locks are available in both fail-safe and fail Secure mode. Fail-safe electromechanical/Electrified Mortise locks are usually used in places like stairwells that usually remain locked.  Fail-secure Electromechanical locks are used in critical room applications like a Server room, main entry, etc.   These doors, when powered, allow people to leave the building but do not allow them to re-enter. However, when there is a fire or some other distress, the door is unlocked with the help of a fire alarm.

 Electromagnetic locks are only available as fail-safe locks. Special release devices have to be attached to one side of the door to unlock the doors during a fire. 

 There are two ways to electrify existing exit devices, latch retraction and panic trims. Fail-safe electrified trims are usually used in stairway fire exits and provide reentry. Indoors where reentry is not required, fail-secure locks can be used comfortably. This is very much like the electromechanical lock system. Electric latch retraction is only available as fail secure locks. They are usually used on exterior doors. But, they need an extensive supply of power. In areas where simple access control is sufficient, electrified trim devices are preferred as they are cheaper than latch retraction devices. 

 Written by Haritha S.