Explosions occurring in enclosures can be found in many technological applications such as internal combustion engines and typical chambers contacting combustibles. However, it is also possible to reach these events in facilities and buildings because of the leakage of a flammable gas, with usually devastating consequences. In this respect, vents are designed to relief the explosion-associated overpressures by allowing part of the fuel mixture gas to evacuate as the flame propagates. In the present work, a computational model is developed to analyse such vented explosion scenarios. The model solves the corresponding governing equations in a single-zone approximation, including the external explosion produced once the vented mixture is ignited by the expanding flame, to calculate the attained overpressures in relation to the domain geometry and burning conditions. A parametric study is performed varying the container dimensions and shapes, given by cuboids and cylinders with central and rear ignition locations, as well as the concentrations of a hydrogen-air fuel mixture. Moreover, different flame velocity expressions are employed to account for a variety of effects influencing the flame dynamics. A mitigating effect of the vent on the enclosure explosion intensity is demonstrated, thereby relating the different conditions to the attained burning regime, essential for the establishment of safety considerations in these partially confined enclosures. (C) 2015 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.