In lockout/tagout, what is the practical difference between applying a lock and applying a tag?

• A. A lock physically prevents energization; a tag only communicates that the equipment is locked out
• B. A tag physically prevents energization; a lock only communicates the status
• C. Locks are optional; tags required
• D. They are equally effective in isolation

Answer: (A)

The key idea is physical isolation versus a warning. A lockout device is a tangible barrier that, once applied to the energy source (like a circuit breaker, switch, or valve), prevents re-energization by physically blocking the mechanism. A tag, on the other hand, is a warning that communicates that the equipment is locked out and who applied it, but it does not stop the energy from flowing by itself. If someone ignores or bypasses the tag, energy can still be supplied, so the tag alone isn’t a reliable method of isolation.

That’s why the correct choice says a lock physically prevents energization while a tag only communicates the status. In practice, locks and tags are used together to provide both a physical barrier and clear warning, but the fundamental difference remains: locks stop energy; tags warn about the lockout.