Qualitative versus quantitative risk assessment

This paper compares the qualitative and quantitative risk assessment methodologies and discusses the common issues associated with the different risk assessment methodologies. The discussion is conducted in the context of UK health and safety risk tolerability framework and a typical risk assessment process. The qualitative risk assessment, although it does not generate results that can be directly compared against the numerical risk tolerability criteria, if conducted properly, can offer valuable insights in distribution of individual risks and help prioritize effort to reduce risk. The quantitative risk assessment, on the other hand, generates risk measures that can be directly compared against the risk tolerability criteria, but there are various sources of uncertainty that would affect the accuracy of the results obtained from the assessment. Qualitative and quantitative risk assessments are not mutually exclusive. One would be more suitable than the other when assessing the risk for different facilities, or the different lifecycle stages of the same facility.