Which of the following constitutes an Independent Protection Layer (IPL)?

Independent Protection Layers (IPLs) are critical components in risk management, specifically within the context of Layer of Protection Analysis (LOPA). They are designed to reduce the likelihood of a hazardous event occurring or to mitigate the consequences if such an event does happen. For a protection layer to be considered truly independent, it must operate separately and effectively from other risk control measures, addressing potential failures in both the primary safety systems and the safeguards designed to protect against hazardous scenarios.

The correct answer highlights a structurally sound barrier, which exemplifies an IPL because it provides a physical means of preventing or mitigating the impact of a hazardous event. A structurally sound barrier can effectively isolate hazardous materials or conditions from personnel or the environment, thereby serving as a tangible control measure that does not rely on human action or compliance to function.

In contrast, while an external review system, procedure manual, and company policy can provide valuable guidance and support in risk management, they do not possess the same level of independent and physical protective capability. An external review system may offer oversight or verification, but it is not a direct mitigative layer. A procedure manual provides instructions but relies heavily on adherence by personnel. A company policy outlines behavioral expectations but is not a physical barrier or direct means of