What is a lock-out/Tag-out device?

• A. A device to monitor temperature.
• B. A device used to physically lock out energy sources and apply a tag indicating maintenance is in progress.
• C. A device to log maintenance records automatically.
• D. A device to measure vibration.

Answer: (B)

Preventing accidental energization during service is the primary safety goal. A lock-out/tag-out device is used to physically lock out energy sources and apply a tag indicating maintenance is in progress. The lock secures the energy‑isolating device (like a switch, valve, or circuit breaker) so it cannot be operated, while the tag communicates that the equipment is under maintenance and should not be energized until the lock is removed by an authorized person. This combination protects workers from injuries that could result from unexpected startup or the release of stored energy. It’s not about monitoring temperature, automatically logging maintenance records, or measuring vibration, which are separate functions.