A series of vented explosion tests were performed in a small-scale cylindrical vessel using a short discharge duct. Overpressure-time profiles were recorded with, five transducers both inside and outside of the vessel. Visualization of the flow field is provided by a high-speed shadowgraph imaging system using sequential shadowgraphs. As is well known, two or more pressure peaks can occur during explosion venting, one from the vent rupture and the other from a secondary explosion induced by combustion of the vented combustible gases. Three typical distinct processes of vented explosions were found. Variations in intensity of the secondary explosion were measured as a function of vent burst pressure, ignition location, blockage ratio at the vent, and equivalence ratio of the fuel. (c) 2006 American Institute of Chemical Engineers