The term barrier is defined as follows: “Physical or engineered system or human action (based on specific procedures or administrative controls) that is implemented to prevent, control, or impede energy released from reaching the assets and causing harm.” Within many industries, the concept of barrier has been widened significantly over the last few years and more and more is being labeled as barriers. Consider the hazardous event “Gas leak from process plant.” Some examples of what is being called barriers related to this event are as follows:

Leak testing of the system to identify leaks after work has been performed on the system. Personnel that are present when the system is being started, to visually or audibly identify any leaks. Training of the personnel performing the work on the system. Procedures that describe how the work on the system should be performed. The work permit system that ensures that maintenance activities are coordinated with other activities, to ensure that they do not influence each other and potentially cause problems. The accident and incident reporting system that is used to report among others all leaks that have occurred from the system. The gas detection system that detects gas leaks. The fire water system that cools equipment in case of a fire and that may extinguish fires.

Discuss these points in relation to the definition provided and decide whether it is reasonable to call all of these barriers? Consider also the defense-in-depth principle, where “the goal is to create and maintain multiple barriers that will compensate for potential human errors and mechanical failures, so that no single layer, no matter how robust, is relied upon exclusively.” Can all of the points aforementioned be considered as additional barriers in accordance with this principle?