Reliability problems in intrinsically safe systems in the context of ATEX directive

The notion: intrinsically safe electrical system (ISES) has been defined in European Standards and refers to the technical elements, interconnected in a system which has intrinsically safe (IS) ratings as required by standards and regulations. Intrinsic safety is achieved through proper selection of components in view of their reliability, through fulfilling suitable constructional requirements, and through proper determination of the parameters of electrical circuits of the ISES in the predicted service conditions. With the undertaking of the problem of safe application of the ISES and attempts at modelling the system from the point of view of safety, the notion ISES assumes a wider sense. Also required is a discussion of the relation between the theory of reliability and the theory of safety. These problems are discussed in context of the new ATEX Directive: 94/9/EC.