Risk analysis is being used to evaluate and manage the potential of unwanted events in the chemical processing industry. The risk in this study is the risk posed by chemical plant accidents and it is presented in a simple quantitative form. A safety risk index is formulated that represents the maximum number of people that might be affected if an accident occurred that caused the release of all the plant inventory of a chemical. The index has four terms: frequency of accidents; hazardous effect of the chemical; inventory of the chemical released; size of the plant. The overall unit of the index is expressed as the number of people affected per year from the plant operation and is formed in a particularly simple manner so as to be suitable for the comparison of safety risk within a model for planning the development of the petrochemical industry.