What is an example of a mechanical lockout device?

• A. A safety cone.
• B. A warning label.
• C. A fuse.
• D. A padlock placed on a circuit breaker or valve that prevents energization until removed.

Answer: (D)

Lockout involves physically securing an energy-isolation point so machinery cannot be started while maintenance or repair is done. A padlock placed on a circuit breaker or valve is a classic mechanical lockout device because it directly blocks the energy source from being re-energized. The person performing the work uses a lock, and only they (or someone with their key) can remove it, ensuring the equipment stays de-energized until it's safe to resume work.

Other options don’t provide that physical, ongoing protection. A safety cone helps people notice a hazard but doesn’t stop the machine from energizing. A warning label communicates risk but doesn’t prevent energization. A fuse can interrupt current, but it’s not a lockout device and isn’t reliably controlled by the person doing the maintenance. The lockout approach is the key idea for preventing unexpected energization during service.