Abstract: In quantitative risk analysis usually generic hypothesis concerning the loss of containment initiating events are applied, in order to simplify the analysis. For example, for the loss of containment from a storage tank: instantaneous release of the complete inventory, continuous release of the complete inventory in 10 min and continuous release from a hole with a diameter of 10 mm. Once these initiating events specified, it is necessary to develop the corresponding event trees to establish which are the different sequences –depending on the properties of the released material, the existing safety barriers, etc.– leading from each initiating event to the diverse final outcomes or accident scenarios. In this communication a set of generic short event trees are proposed for the main cases which can be found, as a function of the type of hazardous material released. Values for the corresponding intermediate probabilities (immediate ignition, delayed ignition, flame front acceleration, BLEVE, etc.) are also proposed, following both a literature survey and expert judgment.