Trapped Key: Where did they come from, where will they go? These risk reduction measures have an interesting history, and we’d like to think an interesting future too.


Trapped Key systems can be used to enforce LOTO procedures, to control access, or to avoid unexpected start-up.


Trapped Key is referred to across a range of machinery safety standards, from ISO 14119 & ISO/TS19837 on the devices themselves, to their inclusion in ISO 14118 on the prevention of unexpected start-up, and more.




✅ Enforce LOTO


✅ Control access


✅ Prevent unexpected start up


✅ ISO 14119, ISO/TS 19837 & ISO 14118


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Trapped Key Standards Today


References & Use Across Standards: 

  • ISO 14119 / IS 16812 – Interlocking Devices
  • ISO  / TS 19837 – Trapped Key Interlocking Devices
  • ISO 14118 / IS 16813 – Prevention of Unexpected Start-Up
  • Standards Relating to the Control of Hazardous Energy

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Use of Trapped Key – Application


Clay Mixer for Roof Tiles

Situations requiring different types of access: 

  1. Inspection
  2. Maintenance

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Trapped Key – Not Just Mechanical


Mechanical approaches have many benefits

RFID Keys can be as proactive inhibit functions.

Keys can be released only when the machine is in the correct state.

Interlock could be unlocked only when Key has been removed – ensuring proactive inhibit function is used.

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