Which safety practice is used to ensure a machine remains de-energized during maintenance?

• A. Guard rails
• B. Procedural risk assessment
• C. Lock out tag out
• D. Personal protective equipment

Answer: (C)

Controlling hazardous energy during maintenance relies on locking and tagging energy-control points to prevent any startup or release while someone is working on the equipment. Lockout and tagout place a physical lock on switches, valves, or other energy-releasing devices, keeping them in the off position and clearly marking that maintenance is in progress. The locks are unique to the authorized worker, and multiple energy sources may require locking for a single machine. A tag provides essential information about who placed the lock, the reason, and the date; it serves as a warning in case a lock is overlooked. Before work begins, the energy sources are isolated, locked, and tested to verify that the machine is de-energized. The device is not removed until maintenance is finished, and only the person who placed the lock can remove it, after confirming that there is no hazard and the machine can be restarted safely.

Guard rails are protective barriers that help prevent physical access, but they do not ensure the machine is de-energized. A procedural risk assessment identifies hazards and controls but does not itself secure energy sources. Personal protective equipment protects the worker from injuries but does not prevent the machine from energizing. Lockout tagout directly prevents unexpected energization, which is why it is the best safety practice for maintaining a de-energized state.