An accidental hydrogen release in equipment enclosures may result in the presence of a detonable mixture in a confined environment. To assess the value of CFD techniques as a tool for damage assessment, numerical simulation of detonation was performed for two realistic scenarios. The first scenario starts with a pipe failure in an electrolyzer, resulting in a leak of 42 g of hydrogen. The second scenario deals with a failure in a reformer where 84 g of hydrogen is released. Dispersion patterns were first obtained from separate numerical simulation and detonative ignition was simulated by adding energy to a narrow region. impulse values reached 600 Ns/m(2) in the electrolyzer scenario while they reached 1100 Ns/m(2) in the reformer. For all cases studied, the consequences are more serious in the reformer than the electrolyzer. (C) 2009 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.