A method for determination of hazardous zones for hydrogen installations has been studied. This workhas been carried out within the NoE HySafe. The method is based on the Italian Method outlined inGuide 31-30(2004), Guide 31?35(2001), Guide 31-35/A(2001), and Guide 31-35/A; V1(2003).Hazardous zones for a ?generic hydrogen refuelling station?(HRS) are assessed, based on this method.The method is consistent with the EU directive 1999/92/EC ?Safety and Health Protection of Workerspotentially at risk from explosive atmospheres? which is the basis for determination of hazardouszones in Europe. This regulation is focused on protection of workers, and is relevant for hydrogeninstallations, such as hydrogen refuelling stations, repair shops and other stationary installations wheresome type of work operations will be involved. The method is also based on the IEC standard andEuropean norm IEC/EN60079-10 ?Electrical apparatus for explosive gas atmospheres. Part 10Classification of hazardous areas?. This is a widely acknowledged international standard/norm and itis accepted/approved by Fire and Safety Authorities in Europe and also internationally.Results from the HySafe work and other studies relevant for hydrogen and hydrogen installations havebeen included in the case study. Sensitivity studies have been carried out to examine the effect ofvarying equipment failure frequencies and leak sizes, as well as environmental condition (ventilation,obstacles, etc.). The discharge and gas dispersion calculations in the Italian Method are based onsimple mathematical formulas. However, in this work also CFD (Computational Fluid Dynamics) andother simpler numerical tools have been used to quantitatively estimate the effect of ventilation and ofdifferent release locations on the size of the flammable gas cloud. Concentration limits for hydrogento be used as basis for the extent of the hazardous zones in different situations are discussed.