This paper discusses the results of validation of Computational Fluid Dynamics (CFD) modeling of hydrogen releases and dispersion inside a metal container imitating a single car garage based on experimental results. The said experiments and modeling were conducted as part of activities to predict fuel cell vehicles discharge flammability and potential build-up of hydrogen for the development of test procedures for the Recommended Practice for General Fuel Cell Vehicle Safety SAE J2578. The experimental setup included 9 hydrogen detectors located in each corner and in the middle of the roof of the container and a fan to ensure uniform mixing of the released hydrogen. The PHOENICS CFD software package was used to solve the continuity, momentum and concentration equations with the appropriate boundary conditions, buoyancy effect and turbulence models. Obtained modeling results matched experimental data of a high-rate injection of hydrogen with fan-forced dispersion used to create near-uniform mixtures with a high degree of accuracy. This supports the conclusion that CFD modeling will be able to predict potential accumulation of hydrogen beyond the experimental conditions. CFD modeling of hydrogen concentrations has proven to be reliable, effective and relatively inexpensive tool to evaluate the effects of hydrogen discharge from hydrogen-powered vehicles or other hydrogen containing equipment.