In lockout-tagout procedures, what is the primary function of a lockout device?

• A. To indicate that equipment is hazardous.
• B. To record the maintenance activity.
• C. To monitor temperature.
• D. To physically secure the energy isolation, preventing energization or re-energizing of equipment.

Answer: (D)

The key idea is to prevent the equipment from being energized while work is being done by using a physical lock on the energy isolation point. This lock physically secures the energy-isolating device (like a switch, breaker, or valve) in the off or safe position, so even if someone attempts to re-energize the system, it cannot be energized until the authorized person removes the lock. This provides positive control of hazardous energy for the duration of maintenance. The lockout device is not meant to indicate hazards (that’s the job of warning tags), nor to record maintenance activity, nor to monitor conditions like temperature.