During maintenance, what safety measure involves applying physical locks to equipment to prevent restart?

• A. PPE only
• B. Electrical interlock
• C. Written permit to work
• D. Lockout-tagout (LOTO)

Answer: (D)

The safety measure being tested is locking out energy sources to prevent unexpected restart during maintenance. Lockout-tagout (LOTO) combines isolating all energy sources connected to equipment with a physical lock and a warning tag placed by the authorized worker. The lock prevents the energy source from being re-energized, and the tag communicates that the equipment is under maintenance and must not be operated. Only the person who applied the lock can remove it, after the work is finished and all safety checks are complete. This approach directly prevents restart or energization, protecting workers from shock, release of stored energy, or startup hazards.

PPE only protects the worker but doesn’t stop equipment from restarting. An electrical interlock may prevent energizing by design, but it’s a built-in device, not a worker-applied safety procedure for maintenance. A written permit to work authorizes the job but doesn’t itself physically prevent a machine from being restarted. Lockout-tagout provides the explicit, enforceable method to ensure equipment stays de-energized during maintenance.