Human reliability refers to the ability of humans to perform a task under given conditions for a given time interval in the range of an accepted limit. The human being can be understood as a system element of the working environment, described as a man-machine system (MMS) and this independently of the complexity of the machine. The MMS determines the reliability and safety of a system. By considering the interaction of man and machine, including the knowledge of the specific properties and capabilities of the human being, a reliable and safe functioning of the overall system can be achieved and maintained. The standard describes the fundamental knowledge a