Experiments were conducted on the vented explosion of hydrogen-air mixtures from a 150-cm-long duct to a cylindrical vessel with a vent at the center of its side wall to investigate the effects of vent burst pressure and an obstacle in duct on the process of explosion venting. Turbulent pressure oscillation owing to a pressure wave moving back and forth in a duct and vessel was observed for unvented explosions. For explosion venting from duct to vessel, flame acceleration in duct much increases the explosion overpressure in vessel. The maximum explosion in duct is always higher than that in vessel, and both of them increase with an increase in the vent cover thickness. An obstacle installed in duct significantly affected the explosion overpressure, which first increased and then decreased with an increase in the blockage ratio. Three pressure peaks were distinguished in the external pressure-time histories, which were resulted form different pressure waves formed outside the vessel. (C) 2018 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.