Last edited 09 Jan 2026

Fail safe

The definition of a fail-safe is 'A design characteristic by which a unit or system will become safe, and remain safe, if a system or component fails or loses its activation energy.' (US Department of Energy)

Fail-safe systems prioritise safety over continually trying to function, so the systems just stops leaving the mechanism open and less harmful. For example a fail-safe door lock would become unlocked during a power outage to ensure emergency exit is possible or a gas valve that may default to closed in the event of a malfunction to ensure there are no leaks. The latter which leaves the system closed under a malfunction might also be referred to as a "fail-secure" system, because it remains locked under failure rather than free.

Designing Buildings Anywhere

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