We have studied the reports from four Nordic companies which did safety analysis of the same system. The system's safety requirements were based on the EN 954 series and the system is required to comply with this standard's requirements for category 4. We wanted to study what they did the same way, what they did different and how the differences influenced their assessment of the system. We went through each company's report and compared the methods used and the results obtained. These results were then compared – noting what was equal and what was different. They often used different methods and if they used the same method, it was used in different ways and focussing on different part of the system. When they identified the same safety problem, they used different term to describe it and it was thus problematic to compare the results. In order to control that a safety analysis is done according to a specified international standard we need to specify analysis methods, how they will be used and the vocabulary to use when describing the results.