BLOG: Fail safe and fail secure - where to use which lock
Access control means very little without robust locking solutions. If the door or gate isn’t securely fixed, it won’t effectively limit who can gain access. Locks are at the heart of physical security. It’s essential that the right lock is chosen for every project.
One of the key decisions when selecting a locking solution for an access control project is that between fail safe and fail secure locks. Some lock types are always fail safe (like electro-magnetic locks) and some may be adjustable between each mode (like some electric strikes). But how do you know which type is right for each project?
What does fail safe mean?
Fail safe locks need power to be applied to lock the door. When there is no power, the door is unlocked. If a door needs to be kept locked all the time, then a fail safe lock requires constant power to remain locked. When a person presents a valid credential (such as inputting the right keypad code or swiping the right card), the power to the lock is temporarily cut. At this point, the locking mechanism drops, and the door can be freely opened.
What does fail secure mean?
Fail secure locks need power to be applied to unlock the door. Without power, the lock remains secure. It’s only when the door needs to be opened that power is applied for a short time to the lock in order to move its mechanism and allow the door to be opened. After the door has closed again, the power to the lock drops. The door then stays closed and locked until the next time someone approaches to enter.
Where should you use a fail safe lock?
A good way to remember the difference is: fail safe locks are designed to keep people safe. When power is lost, fail safe locks are unlocked. So if there was an emergency that caused a power cut, all the doors with fail safe locks would be free to open. For example, if a fire in a building made the power cut out, all the people inside would be able to get out easily through an unlocked fail safe door.
Fail safe locks are therefore best suited to external doors, emergency exits, and stairwell doors. Any door that must allow free movement in the event of a fire alarm or power failure should have a fail safe lock.
Where should you use a fail secure lock?
On the other hand, imagine that you had a bank vault that was secured with a fail safe lock. In an emergency, the power cuts out and your bank vault is suddenly unlocked, with no way to re-lock it without electrical power. That’s why you should always use fail secure locks to keep assets secure.
The default position of a fail secure lock is locked. That’s why they are best suited for areas containing valuable assets or sensitive data. IT server rooms, finance offices, and stock rooms are commonly equipped with fail secure locks.
What kind of locks are fail safe?
All electro-magnetic locks are fail safe by their nature. Without power, the magnet doesn’t produce the magnetic field that holds the door closed. It’s only when electricity is run through the magnet that its magnetism is activated and the force holding it to the armature plate is generated.
Some electric strikes and electro-mechanical locks are fail safe either as standard or as an option. Some strikes and locks can be switched between fail safe and fail secure modes, depending on the requirements of the project.
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What kind of locks are fail secure?
Fail secure locks are the most common type. Most organisations are concerned about security. In the event of a power cut, they want their building and the equipment and data kept within it, to be secure. If a whole building had fail safe locks throughout, then in a power cut anybody could walk in and around freely.
Electric strikes and electro-mechanical locks are almost always fail secure as standard. Some models may be mode-adjustable, meaning they can be switched to fail safe mode if required.
Power consumption – another consideration
Another consideration when selecting locking types is that of power consumption. If you need to apply power constantly to a fail safe lock to keep it locked, then it’s going to be more expensive to run. Here is an example.
Let’s say your fail safe lock requires 480mA at 12Vdc power supply to run. And let’s say you’re applying power 23 hours a day, with an hour spare covering all the times people use the door and the power drops.
480mA is equivalent to 5.76 Watts. The current cost of 5.76W for 23 hours of runtime is a little bit less than five pence*. That doesn’t sound like too much. But multiply that by 365 days in a year, and the annual running cost is about £16.50 for that one lock.
If you’ve got 50 locks in your building, that would cost you over £800 a year to power them.
Let’s compare that to a fail secure lock. We’ll keep the power consumption and voltage the same. And let’s say the lock requires power for 1 hour out of every 24 to allow people to gain entry.
Assuming the same electricity costs, that fail secure lock would cost less than a penny a day to power. In fact, for an hour a day of average usage over the whole year, it would cost just 71p. For your 50 locks, that’s a saving of £786.50 every year.
Cost is of course not the only consideration. Safety and security are both extremely important. On emergency exits and escape routes, fail safe locks should be used regardless of cost implications. The inclusion of power consumption and associated costs in this blog is only for illustrative purposes. Qualified installers should select the most appropriate lock type and mechanism for each door based on the best-suited combination of safety and security requirements.
*Costs calculated at the time of writing on 16/02/23 using sust-it.net.