In order to reduce green house gases, hydrogen fueled vehicles are expected to be commercialized in the near future. Hydrogen is nontoxic, but it is flammable. A relatively low ignition energy can ignite a hydrogen-air mixture when the concentration of hydrogen is within a flammable range. Therefore safety concerns related to possible leakage from hydrogen fueled vehicles need to be addressed. In this study, we focus on the distribution of the lower flammability limit (LFL) of a hydrogen cloud when hydrogen is released from a fuel cell vehicle. CFD techniques, using FLUENT, are applied to the simulation of hydrogen dispersion from a parked vehicle's tailpipe. We analyzed several hydrogen release scenarios to investigate the hydrogen cloud formation, thermal effects and transient behaviors. We also simulated the effects of the inclination of the garage ceiling and forced ventilation on hydrogen dispersion. We found that the configuration of indoor space affects the hydrogen cloud formation in certain ways. The simulation results can be further applied to define the codes, standards and recommended safety practices related to possible hydrogen leakage and the risk of ignition.