In order to improve risk analyses and influence the design of the future H-2 systems, an experimental study on "real" leaks qualification and quantification was performed. In H-2 energy applications, fittings appeared as a significant leakage potential and subsequently explosion and flame hazards. Thus, as a part of the "Horizon Hydrogene Energie" French program, four kinds of commercial fittings usually employed on H-2 systems were tested thanks to a new high pressure test bench designed, setup and operated by INERIS - allowing experiments to be led for H-2 pressures until 700 bar. The fittings underwent defined stresses representative of H-2 systems lifetime and beyond. The associated leaks when existing are characterized in terms of flow rate. Copyright (C) 2012, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.