Ranking Chemicals with Respect to Accidents Frequency

Abstract

The chemical industry is one of the most well-known high-risk areas in modern society. Chemical accidents can have a great and lasting impact on the public’s perception of a chemical facility’s risk. The number of reported accidents constitutes a natural direct source of information on accidents risk. Reports provide a better understanding of two risk criteria, frequency and consequence, and help to identify hazardous chemicals, which can thereafter prevent accidents. Many published risk and accident data reports give information on the number of accidents or the numerator of the frequency calculation. However, they appear blind to information on exposure, such as the scale of the facility operation (the frequency denominator). This study will present how neglecting the denominator in frequency calculation gives misleading risk alerts. The research also proposes suitable denominators and a method to combine different frequency data based on partial order. Higher data size is also a good confidence indicator in frequency estimation. Results show that normalization with a suitable denominator is important, and the task is possible with the availability of many accident databases. Furthermore, partial order ranking using the Hasse diagram gives an overall hazard view of chemicals; it was able to estimate the percentage of chemicals performing above acceptable risk using only a small sample size.