This report deals with methods for calculating the physical effects of the escape of dangerous materials. These methods can be used in carrying out safety studies. A full safety study consist of the following: the identification of undesirable events in which hazardous materials are involved, determining the magnitude of the physical effects, determining the damage which can be caused by them, determining the probability of that damage, estimating the objective risk and evaluating the risk. This report deals only with the part determining the magnitude of physical effects.