Fail-Safe vs Fail-Secure Locks: Access Control Design Guide
Every electric door lock must decide what to do when power fails. A fail-safe lock unlocks. A fail-secure lock stays locked. The right choice is different for a fire exit, a server room and a main gate, so it belongs in the access control design from the start, not at the end.
Key takeaways
- Fail-safe locks open when power is lost; fail-secure locks stay locked.
- Escape routes and people-safety doors usually need fail-safe behaviour.
- Stores, server rooms and secure areas often use fail-secure locks with free exit.
- Fire rules and local codes decide the final choice, not the lock catalogue.
- Test every door in a power-off drill before the system goes live.
What fail-safe and fail-secure mean
The two terms describe the lock state when it loses power. The table sets them side by side.
| Lock behaviour | With power off | Typical use |
|---|---|---|
| Fail-safe | Door unlocks | Escape routes, stairwells, doors on exit paths |
| Fail-secure | Door stays locked | Server rooms, stores, secure areas |
Do not confuse these with fail-open or fail-closed network behaviour. Here the question is only what the physical lock does.
Where each lock type fits on a site
Start from the purpose of each door. If people must always be able to leave quickly, choose fail-safe or make sure a mechanical release is always available. If the room protects assets, choose fail-secure and keep a free exit on the inside through a handle or a push bar. Mixed sites use both, and the door schedule should state the choice for every opening.
Power cuts, backup supply and door behaviour
Backup power changes the picture. A small battery supply keeps readers and locks working through short outages, so doors behave normally for a while. After that, the lock default applies. Decide how long backup must last, and what staff do when it ends. Controllers should store access rights locally so doors keep working if the network link to the server drops.
Fire alarms, exit routes and safety rules
Fire safety rules sit above security wishes. Many sites connect doors on escape routes to the fire alarm panel so they release when the alarm sounds. Local fire and building codes apply, so involve your fire safety officer or consultant when you decide which doors release and how. Never rely on a card read alone for the only way out of a space.
Testing door behaviour before go-live
Write a simple test sheet with one line per door. Switch off power to the lock, then check the door state. Trigger the fire alarm input, then check the release. Drop the network link, then confirm the card still works. Record the result, fix any door that behaves differently from the design and repeat the test after changes. Our overview of how an access control system works shows where each part sits.
Planning door failure modes with Suraj Informatics
Suraj Informatics plans access control with a door schedule that states the lock type, power backup and fire release for every opening. Send us your floor plan and we will help you draw it up.
Fail-safe vs fail-secure locks: common questions
Which lock is more secure?
A fail-secure lock stays locked in a power cut, but safe exit still has to be provided. Security never overrides life safety.
Can one site use both types?
Yes. Most sites do, choosing the lock for each door by its purpose.
Do magnetic locks fail safe?
Magnetic locks release when power is removed, so they behave as fail-safe. Check the model and your local rules.
Who decides the final choice?
The design team with your fire safety officer, following local fire and building codes.
Talk to our access control team
Share your door list and floor plan, and we will help you choose a lock behaviour for each opening.
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