IMPROVED F/N GRAPH PRESENTATION AND CRITERIA

The hazards attending a process from which hazardous materials could be released can be assessed in terms of frequency of casualty-causing incidents and the number of casualties in each such incident. Historical data for accidents can be graphed in the form of frequency versus number of casualties (F/N) curves, for use in assessing public exposures to various types of accident, including transportation and industrial incidents. Similar curves can be constructed for industrial exposure of employees. These can be used to determine the need for process improvement and in assigning priorities for recommendations, The resulting 'two-dimensional' graphical presentation can be used to show 'existing' and 'upgraded' process performance and overcomes some statistical problems of 'one-dimensional' safety assessments and criteria. Appropriate criteria for public exposures would be the historical F/N curve for acts of God or acts of nature, with a suitable safety margin. The curves can be normalized to account for differing numbers of potentially-exposed members of the public or employees, allowing comparison of the hazards encountered in different industries, environments or countries. The development of F/N curves, particularly in Europe, and their probable application in evaluating the effectiveness of process safety management are presented.