The assessment of risks related to the operation of public and non-public hydrogen refuelling stations is a key step in the sitting approval process by legal authorities and eventually fire-department. Present work is underway at European level to facilitate approval procedures in order to ease technology deployment across Europe. In France, the ALTHYTUDE project co-ordinated by Gaz de France, deals with the use of a bus fleet fuelled with a mixture of hydrogen and natural gas in two different cities. Dunkerque in the North of France (two busses) and Toulouse in the South of France (three busses) have been selected. Refuelling stations will be built in each city. So as to get the sitting approval of the refuelling stations, risks analyses have been performed for each station. These risk assessments are in line with the new French regulation related to major accidents and somehow compatible with the health & safety at work regulation regarding explosion hazards. Methodology and first results of the risk analysis of the Dunkerque refuelling station are reviewed in this paper: hazardous scenarios have been proposed, safety barriers have been listed for each scenario, intensity quotation has been performed and scenario have been chosen for hazard quantification.