The Demon–Angel method in systematic safety assessment

Since `design for safetyʹ of large engineering systems with a high level of innovation requires an exhaustive safety analysis and since a subsequent corrective action may become a very large bottleneck in improving such a system, fundamental knowledge in designing safe systems is essential. The lack of any `rule of thumbʹ makes such knowledge a matter of personal experience rather than the subject of an academic course. This paper proposes a new method for the theoretical safety study of different system configurations independently of any particular application. This method aims to help the construction of a `rule of thumbʹ for what is a safe system and what is not. The Demon and Angel ideas are explained and the schematic presentation of these elements is introduced. Four representative case studies demonstrate the use of this method.