Sammanfattning I avhandlingen Decision Analysis in Fire Safety Engineering – Analysing Investments in Fire Safety undersöks hur beslutsanalytiska modeller kan användas för att utvärdera olika investeringar i brandskydd för en specifik industribyggnad. En stor del av arbetet behandlar hur den riskreduktion som en investering i brandskydd medför kan värderas i form av ett monetärt värde och hur man kan hantera stora kunskapsosäkerheter rörande sannolikheter och konsekvenser. Abstract The application of decision analytical methods to the evaluation of investments in fire safety was investigated, particularly with the aim of being able to suggest a method for analysing a specific investment in fire safety for a specific factory. Attention was directed above all at the handling of cases of large epistemic uncertainty regarding both probabilities and utilities, Bayesian decision theory serving as a basis for the development of the method. Two extensions of the decision rule used in Bayesian decision theory (the principle of maximising expected utility) were suggested for use in the present context. Together with a model for calculating the expected utility of a specific investment, they provide an evaluatory framework for the analysis of investments in fire safety. The major contributions of the thesis to the area of decision analysis within fire safety engineering are that it provides a better understanding of the use of different decision analytical approaches in a context such as the present one, that it highlights problems of evaluation when large epistemic uncertainties are present, that it suggests a solution for use in such a case, and that it suggests