Informational
Fail Safe vs Fail Secure
Explainer Guide
These two terms sound simple, but they shape the whole lock path of the job. They affect which hardware is chosen, how power is supplied, what happens in faults, and what the client expects when the building loses normal mains power.
What It Means
Fail safe usually means the locking device releases when power is removed. Fail secure usually means the door remains locked when power is removed. That sounds straightforward, but it is only useful when you look at the whole opening: the lock type, egress path, emergency release logic, door closer performance, and how the site actually wants the door to behave.
Text Diagram: Power-Loss Behaviour
[Normal power present]
|
+--> [Fail safe path] ----> Door stays locked while powered
| Door releases if power is removed
|
+--> [Fail secure path] --> Door unlocks only when commanded
Door stays locked if power is removed
Quick Fit Guide
| Question | Fail Safe Thinking | Fail Secure Thinking |
|---|---|---|
| What happens if power disappears? | The lock path releases. | The lock path remains secure. |
| Where is it often discussed? | Main-entry maglocks, some intercom doors, some doors needing release on loss of power. | Office doors, store rooms, records rooms, and other openings where security must not disappear just because mains power drops. |
| What must the installer verify? | That the release outcome matches the full egress and emergency logic for the opening. | That the site still has a safe exit path and understands the difference between secure-side entry control and exit requirements. |
How It Fits in a Real Installation
A good installer does not pick fail safe or fail secure from habit. They survey the real opening. A glazed front door with an intercom and a maglock will often lead to a different outcome than a rear records-room door with an electric strike. The right answer is driven by the full operating model: who uses the door, whether the site wants the door to release on power loss, how egress is achieved, and how the opening is expected to behave during an emergency or controlled shutdown.
Questions That Should Be Resolved Before Quoting
- What should this specific door do if normal power disappears unexpectedly?
- Is the door visitor-facing, staff-only, or protecting a more sensitive room such as records or stock?
- What hardware is actually on the opening now: latch, closer, frame depth, glazing, and cable path?
- Is the site expecting UPS backup, and if so, which parts of the door path are meant to stay active?
- Does the site understand the difference between keeping logs alive and keeping the lock energised?
What People Usually Get Wrong
The most common mistake is reducing the conversation to one sentence such as âÂÂI want it to stay locked if the power goes outâ or âÂÂI want it to unlock if the power goes out.â That is not enough by itself. The installer still has to match the lock hardware, the controller logic, the power design, the exit path, and any wider emergency release logic. Another common mistake is assuming UPS automatically solves the design. It can help continuity, but it does not replace the need to decide the correct underlying fail mode.
Useful Positioning Rule
If the client is really asking what happens during mains failure, emergency release, or fault conditions, they are not only asking about a lock. They are asking about door behaviour. Treat it as a full opening-design question, not just a line item.
Relevant SecurityWholesalers Product Areas
- Access Control – Useful for controllers, readers, credentials, and the wider lock-and-door workflow behind the opening.
- Hikvision DS-K2702X-P – A strong fit when one or two doors need proper logs, schedules, and a cleaner controller-led architecture behind the lock decision.
- Hikvision DS-K2704X – Useful when several doors, lift control, gates, or future growth mean the fail-mode discussion should sit inside a broader controller-based system.
- Hikvision DS-KV6124-WBE1 – Relevant for visitor-facing front doors where intercom, credential entry, and the lock-release workflow need to live together.
Related Guides in This Series
- Electric Strike vs Magnetic Lock
- Fire Alarm, Emergency Egress, and Door Release Logic
- Strikes, Maglocks, Exit Buttons, and Door Sensors
Source References
- SecurityWholesalers: Access Control
- SecurityWholesalers: DS-K2702X-P
- SecurityWholesalers: DS-K2704X
- SecurityWholesalers: DS-KV6124-WBE1
Frequently Asked Questions
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What does fail safe versus fail secure mean in plain English?
Fail safe usually unlocks when power is removed, while fail secure usually stays locked when power is removed.
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Does fail safe automatically mean maglock and fail secure automatically mean strike?
Not automatically. Many maglock jobs are fail safe and many strike jobs are fail secure, but the real answer depends on the full door, lock, release, and egress design.
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Why is this decision so important at quote stage?
Because the power-loss behaviour affects lock selection, power supply design, emergency release logic, user expectations, and fault handling.
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What is the most common buyer mistake here?
The most common mistake is asking for a lock outcome without first confirming how the door should behave during power loss, emergency release, and normal egress.
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Should UPS planning change this decision?
UPS can support continuity, but it should not be used to dodge the fundamental decision about how the opening should behave if normal power is gone.
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Which related guide should I read next?
Read the electric strike versus magnetic lock guide next, then the fire alarm and emergency egress explainer.