Numerous accidents are due to situation awareness degradation. However, as there exist many different causes and human factors are not well understood, it is very difficult for experts to provide probability risks assessments. It is proposed here to simplify the problem by classifying accidents according to the main demons that degrade situation awareness and to use a Bayesian approach with the Noisy-Or nodes. Interestingly, it is possible to use the same approach in the robotics domain.