Since a few years, hydrogen appears as a practical energy vector and some hydrogen applications are already on the market. However these applications are still considered dangerous, hazardous events like explosion could occur and some accidents, like the Hindenburg disaster, are still in the mind. Objectively, hydrogen ignites easily and explodes violently. Safety engineering has to be particularly strong and demonstrative; a method of precise identification of accidental scenarios ('probabilities'; 'severity') is developed in this article. This method, derived from ARAMIS method, permits to identify and to estimate the most relevant safety barriers and therefore helps future users choose appropriate safety strategies.