Hazardous areas extension in explosive atmospheres caused by free gas jets

This paper regards the validation procedure of the Italian Guide CEI 31-35 formula, used to calculate the hazardous areas extensions in places where explosive gas atmospheres may be present. In industrial activity, a typical event which cause explosive atmosphere consists of damaging and leakage from unions, gaskets, valves of pipes and vessels. At this purpose, in this work it has been taken into account the accidental discharge of flammable gas into a quiescent atmosphere through an orifice. Validation has been performed by comparing calculated values with experimental data. Two gases have been taken into account: methane and hydrogen. Different scenarios have been analyzed, each one differing from the others in the gas release cross section and in the vessel pressure. Results show that the formula fits well not catastrophic industrial accident situations.