The technical knowledge in the field of non-reactive blast-waves propagation in free field is today well established. A different situation can be noticed for detonation of explosive charges or bursting of pressurized vessels in partially confined spaces such as tunnels or platforms. Several research programs have been carried out in the past years to investigate the effects of detonating charges in underground ammunition magazines but most of the results are obviously kept under military restriction. About the bursting of pressurized vessels, such as LPG road tankers, special attention is paid to the safety of transport from a general point of view and experimental data available are exclusively related to open space accidents. In this paper the simple concept of Energy Concentration Factor (ECF) is introduced to allow the prediction of blast-waves overpressure in partially confined geometries from open space blast data. Despite the simplicity of method, the results show a direct link between intensity of peak side-on overpressure and volume of the region crossed by the blast-wave. © 2009 Elsevier Ltd. All rights reserved.