Which of the following is a criterion for double barrier protection related to sea exposure?

• A. Sea connected systems
• B. Freshwater-only systems
• C. Isolated systems
• D. Submerged but not connected

Answer: (A)

Double barrier protection is about having two independent safeguards to stop seawater or its contaminants from reaching sensitive parts. When a system is sea connected, seawater is part of the exposure path, so you need that extra layer of protection to prevent a single failure from causing intrusion. The first barrier blocks or limits intrusion, and the second provides redundancy or an early alert before anything reaches critical components. If the system isn’t connected to the sea, such as freshwater-only or isolated setups, there isn’t a seawater exposure path to defend, so the criterion for double barrier protection in this context isn’t met. Submerged but not connected might imply exposure in other ways, but the explicit sea connection is what triggers the need for two barriers.