On the modelling and characterisation of safety functions

Different theories and applications concerning "safety barriers" and "safety functions" have been investigated. The general aim was to compare principles and terminology in some different areas. Of special interest are applications from the nuclear and chemical-process industries, and a short summary is given. The study is based on a literature review, interviews and discussions. Only a few theoretical models describing safety functions have been found. This points to the need for further development of models and theories that might provide a basis for improved practical tools to support the design and evaluation of organisational proce dures. A tentative model is discussed. It is based on "safety function elements" and the characteristics needed to describe and assess safety functions, e.g. purpose, efficiency, and reliability.