To provide more practical data for safety assessments, a systematic study of explosion and combustion processes which can take place in mixtures produced by jet releases in realistic environmental conditions is required. The presented work is aimed to make step forward in this direction binding three inter-connected tasks: (i) study of horizontal and vertical jets, (ii) study of the burnable clouds formed by jets in different geometry configurations and (iii) examination of combustion and explosion processes initiated in such mixtures. Test matrix for the jet experiments included variation of the release pressure and nozzle diameter with the aim to study details of the resulting hydrogen concentration and velocity profiles depending on the release conditions. In this study the following parameters were varied: mass flow rate, jet nozzle diameter (to alter gas speed) and geometry of the hood located on top of the jet. The carried out experiments provided data on detailed structure for under-expanded horizontal and buoyant vertical jets and data on pressure loads resulted from deflagration of various mixtures formed by jet releases. The data on pressures waves generated in the conditions under consideration provides conservative estimation of pressure loads for realistic leaks.