Duct vented geometries are a common feature in modern industrial installations where a vessel is protected from internal explosion pressures, and where the explosion products need to be directed away from sensitive areas. In this research, stratified propane-air concentrations have been investigated using a vented vessel connected to a vent pipe. Concentration, injection position and ignition position were varied and comparisons made with homogeneous tests at the same 'global concentration' for each condition. The maximum pressures produced by the worst case stratified mixture were only about a quarter of the maximum produced by the worst case homogeneous mixtures. However, for lean concentrations, stratified mixtures were shown to produce consistently greater pressures than the equivalent homogeneous case, irrespective of ignition position. In addition, results are presented which demonstrate that end ignition appears to be more severe than central ignition, contrary to what is reported in literature.