The external explosion in a stainless cylindrical explosion vessel with the hydrogen air mixture is investigated as the function of the vent burst pressure. The internal and external pressure curves measured by four piezoelectric pressure transducers with three ignition locations are used to analyze the effect of ignition location on the whole explosion venting. It was shown that central ignition always generates the highest internal peak pressure; but the highest external peak pressure always appears on the pressure curve with the rear ignition. The external explosion is demonstrated by the jet flame photographs captured by the high speed camera. As the vent burst pressure increases, it is a general trend that the internal and external peak pressures are increasing accordingly; but just for the rear ignition, it seems that the external peak pressure is less affected by the vent burst pressure. And not only that, the external explosion site remains the same roughly with the change of the vent burst pressure for whatever ignition location. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.