In this work the validity of simplifed mathematical models for predicting dispersion of turbulent buoyant jet or plume within a confined volume is evaluated. In the framework of the HYSAFE Network of Excellence, CEA performed experimental tests in a full-scale Garage facility in order to reproduce accidental gas leakages into an unventilated residential garage. The effects of release velocities, diameters, durations, mass flow rates and flow regimes on the vertical distribution of the gas concentration are investigated. Experimental data confirm the formation, for the release conditions, of an almost well-mixed upper layer and a stratified lower layer. The comparison of the measurements and the model predictions shows that a good agreement is obtained for a relatively longtime gas discharge for jet like or plume like flow behaviour.