In this paper, based of the energy flow/barrier analysis, an accident is defined as failure of the control and protective barriers, which results exposure of a target to a hazardous agent. Barriers combination is modeled as “Barrier structure”, an arrangement of serial and parallel barriers. Using this structure, and by considering barriers reliability and efficiency, the probabilities and severity of varios accidents are estimated. By studing the possible contacts between the different couples of hazards and targets, this approach can be used to generate the different accidents scenarios and to recognize the more critical barriers in the complex environnements.
