Developing Risk Matrix Categories

A risk categorisation model combines hazard categories with exposure categories for the identification of those situations that require most attention to be improved. The risk matrix model which have been developed with the hazard and exposure categorisation given in Sects. 26.3.5 and 26.5.3 will be given as an example. It applies to inhalation risks of small scale pharmacy preparation. This approach is similar to those by the INRS [27] and COSSH [28]. 

To emphasize Safety professionals must understand that the definitions of terms for incident probability and severity and for risk levels vary greatly. Thus, they should tailor a risk assessment matrix to suit the hazards and risks and the management tolerance for risk with which they deal. Examples of the definitions used for incident probability and severity are presented here, as well as definitions for risk categories and risk assessment matrices. They are intended to provide safety professionals with a broad base of information from which choices can be made in developing the matrix considered appropriate for their clients needs. 

From these two data categories a criticality matrix as detailed in Chapter I (in the name of risk matrix) is formed. In many cases, both probability of occurrences and severity categories are numbered in the scale of 1—10 and a criticality matrix can be formed for the same purpose. As these are already covered in Chapter I they are not repeated here. Analysts need to understand that these are for reference only. Analysts use their judgment of failure mode frequency for each specific application. The analyst should tailor the analysis to focus on significant components or subassemblies where failures will result in undesirable system-level effects. Based on these judgments, analysts develop risk categories for the specific application. 

Roland and Moriarty (1990) show how to develop a Hazard Assessment Matrix to determine a Hazard Risk Index using frequency of occurrence and hazard category (see figure 9-3). 

Using these probability and severity categories, a risk analysis matrix can be developed for any type of event and used to identify imacceptable risks for the operation. It can also be used to prioritize which risks wiU be addressed—where action is taken to eliminate or reduce them—and in which order. An example risk-analysis matrix is given in Figure 18.1, with high priority cells identified. The highest priority cells are located in the upper left part of the matrix, while the lowest priority cells are in the lower right corner. The approach could be used to compare the impact of many different events, such as roof faU accidents, rock burst events, and mine fires. It can also be used to combine both quantitative and quahtative risks. 

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