Which describes a passive barrier?

• A. Active barrier that requires action to operate.
• B. Passive barrier functions without action.
• C. Barrier that operates only during maintenance.
• D. Barrier used only in testing.

Answer: (B)

A barrier is protective in nature, and it can work with or without human action or energy. A passive barrier does its job automatically, without needing external energy or operator input. Its protection comes from its physical characteristics or fixed placement—things like a containment wall, bunds, or a space design that keeps hazards separated. Because it operates without having to be turned on, activated, or controlled, it is always in place and ready to do its job.

Active barriers, by contrast, depend on energy or human action to function—alarm systems, interlocks, remote shutdowns, or valves that must be opened or closed in response to signals. They require action to provide protection.

So the statement that a barrier functions without action accurately describes a passive barrier.