In recent years the importance of safety and environmental issues in chemical process design has increased. The idea of inherent safety and 'green' processes has arisen. From this perspective the goal is to design ideal chemical processes that need only minimum amounts of raw materials and energy and that do not require elaborate safety measures and end-of-pipe technologies. While chemical processes are continuously improving in this direction, nowadays safety and end-of-pipe technologies are still indispensable. We developed a concept that in a hierarchical approach reveals the degree of non-ideality of chemical processes with regard to SHE (safety, health and environment) aspects at different layers: the properties of the chemical substances involved (substance layer); possible interactions between the substances (reactivity layer); the possible scenarios resulting from the combination of substances and operating conditions in the various equipments involved (equipment layer); and the safety and end-of-pipe technologies that are required to run a process safely and in accordance with legal regulations (safety technology layer). The method is particularly suited for the early phases of chemical process design. In this paper we focus on the safety aspects of the methodology. With the help of three case studies the overall concept is demonstrated and it is shown how the method reveals the degree of non-ideality of different chemical process aspects with regard to inherent safety. Furthermore, the method helps in identifying those technical measures that have to be taken in order to run the process nonetheless.