ABSTRACT
This chapter introduces the concept of barrier function; physical separation and separation by distance are two examples of such a function. It also introduces other types of barrier functions, all of them with the characteristic of being able to intervene in an accident sequence to prevent or limit loss. The chapter presents a set of criteria similar to those recommended by the Norwegian Petroleum Safety Authority (PSA) that includes capacity, reliability, accessibility, efficiency, ability to withstand loads, integrity, and robustness. It also focuses on criteria related to the prevention of partial or total failure. Barriers, including their subsystems and elements, require regular inspection, testing, and maintenance to ensure reliable performance. The on-scene commander is responsible for combatting the emergency event and limiting loss. The planning of emergency response needs to be based on risk assessment in order to ensure adequate direction and balance of resources.
