In the frame of the OECD/NEA SETH project an experimental campaign has been carried out in the PANDA facility to investigate key physical phenomena relevant for LWR safety analysis. Three series of tests, named wall plumes, free plumes and horizontal jets, have been performed. In addition to these series of tests, one specifie free plume test with steam, air and helium has been performed. The paper summarizes the results of the horizontal jets test series consisting of eight tests. Horizontal jets impinging on a vertical wall have been generated by changing various parameters, such as: type of injected fluid (steam or a mixture of steam and helium), fluid injection velocity, elevation of the injection exit, initial fluid composition in the vessels and location of the vent line inlet. The initial jet Froude number has been varied between 17 and 35. The paper shows the effect of this parameter variation during the test evolution with respect to: jet impingement location and variation of impingement location as a function of buoyancy variation, fluid mixing and stratification, characteristics of gas transport between the compartments and the effect of condensation on the overall phenomena evolution.