In the current work the rhoReactingBuoyantFoam solver was customised for performing gas leak and gas dispersion modelling. Using experimental data from gas leaks the proposed modelling was investigated for subsonic and sonic releases. The gas molar fraction and velocity decay along the jet centreline were calculated using the modified reacting solver, and the numerical findings were compared with available experimental data. Different approaches for the turbulence closure problem were considered using standard two-equation models. The numerical stability of the solver was also investigated varying the CFL number for a set of simulations. The work also considered the modelling of gas cloud volume in a real engineering case. Standard computational setup for ANSYS-CFX was applied, and the same set of scenarios were modelled in OpenFOAM using the modified rhoReactingBuoyantFoam solver. The analysis considered 5 different leak directions and 4 wind directions in a typical industrial site. For all scenarios simulated, very good agreement with experimental data and with the commercial CFD (computational fluid dynamics) tool considered in this study was observed. The results are within 10% tolerance intervals. Detailed information of the modelling is also provided, which enable any CFD user to reproduce the results and also apply it for future analysis. (C) 2016 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.