DEFINITIONS
If there is a power outage in your building, will your main entrance doors be locked on the outside, or unlocked? Will individuals be able to enter the building during a power outage? The answers depend on whether the doors have Fail Safe or Fail Secure locking devices. Building codes require that occupants of a building be allowed to freely leave through emergency exit s (exit sign above the door); however, codes do not require that everyone be allowed to enter a building during an emergency or power outage.
Electrified locking devices are generally classified as either "Fail Safe" or "Fail Secure." A Fail Safe device is unlocked when power is not being applied to it; it requires power in order to lock the door. A Fail Secure device is just the opposite; it remains secure (locked) in the absence of power, and requires that power be applied in order to unlock the door. The use of the term "safe" in this context is often confusing; you might not feel safe in a protected space if the doors unlocked during a power failure; but if the doors "failed safe," you would not have to worry about being able to exit the building.
TYPES
There are various electrified door hardware products that can be used to electronically lock or unlock a door, all of which are commonly used in access-controlled door applications. Typical applications include main and employee entrances and access-controlled doors.
APPLICATIONS
Detex recommends using Fail Secure locking devices for doors that lead to the exterior, so that only authorized personnel are allowed into the building, even during a power outage. However, depending on the jurisdiction and the applications, there are situations that require Fail Safe locks.
For instance, in most jurisdictions, fire-rated stairwell doors must Fail Safe during a power outage, allowing persons in a stairwell to seek refuge on certain floors and giving first responders access to certain floors. Using exit devices with Fail Safe electrified trim is one way to control who has access in high-rise buildings during normal operation, while allowing first responders to access any floor during a power outage or other emergencies. However, it is probably advisable to insure that main entrance doors are always locked during a power outage, allowing entrance only to authorized personnel with the proper key.
POWER CONSUMPTION
Power consumption is also a factor to be considered. Because Fail Safe locks by definition require continuous application of power to keep the door locked, they can be more expensive to operate than Fail Secure locks, which keep the doors secure even when no power is applied.
Although even the most efficient electric latch retraction exit devices still draw approximately 2 amps, keep in mind that this power consumption is brief, lasting only a few milliseconds; and all latch retraction exit devices are Fail Secure. In order for electric strikes and electrified trim to be Fail Safe, they must be constantly powered, drawing less than 1 amp every second of the day. Magnetic locks require constant power, but are always Fail Safe. Electrified dogging exit devices can be used to allow push/pull operation of a door during normal business hours, and is always Fail Secure during a power outage; but they require constant power when dogged (push/pull operation).
