(41b) Identifying Significant Human Factors in Quantitative Risk Assessments

The term human factors refers to characteristics of operators, supervisors, or workers such as level of training, and to characteristics of the working environment. In a large facility, multiple human actions may be credited in preventing accidents and some of the human actions may be dominant contributors to accident sequence frequency. In some cases, the various human actions depend on the same human factors. For example, different operators may all be credited with having adequate training, even though different operators may perform different actions during accidents. Because each human factor can touch several human actions and the number of human actions can be large in a large facility, it can be difficult to identify which human factors are the most significant in preventing accidents. This paper describes a method for rapidly identifying human factors that contribute the most to accident sequence frequency. An example quantitative risk assessment in a hypothetical chemical processing facility is discussed to show the methodology for identifying significant human factors. Accident sequence frequencies within this hypothetical facility are shown to be overestimated or underestimated based on the uncertainty in significant human factors.