Different approaches to risk analysis with a focus on risk estimation and risk evaluation have been compared. Critical aspects of quantitative and qualitative methods and criteria are summarised. An explosives accident has been analysed as an example. The explosion occurred in a system, which was frequently changed and exposed to disturbances. This entailed a number of difficulties in the validity of the results of the performed risk analysis. For example, the actual type of accident was not anticipated. Systems, where changes are frequently introduced as a result of disturbances in the process, offer a number of difficulties in making a risk analysis. Risk assessments, especially those based on probabilistic approaches, could easily be of reduced value, due to a number of reasons. For this type of situations, alternatives to traditional probabilistic assessments could offer advantages. There are a number of qualitative approaches that are interesting to explore further, and a test with Safety Function Analysis appeared to solve some of the problems related to system changes.
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