When considering the consequences of gas explosions in petro-chemical installations simple methods are used such as TNT-equivalency methods and the Multi-Energy method. These methods, however, do not take into account directional effects, focusing effects, factors related to the source of the explosion (initial strength, shape) and reflections. FLACS, a 3-D CFD tool, allows for all factors mentioned including focusing on effects and reflections near buildings. A comparison of the CFD-method including the two traditional prediction methods for a practical case demonstrates the application areas of the FLACS method as well as the limitations of the traditional methods.