Although there are recognised methods for estimating reduced explosion pressures in vented dust explosions, and for taking into account the effect of vent ducts, explosions in powder handling plant often bear little resemblance to explosions produced in standard tests. The aim of the present work was to measure reduced explosion pressures, and the effects of various configurations of vent duct, in dust explosions in dust collectors. The effect of vent ducts was less than predicted by published methods applicable to homogeneous dust clouds, although some published guidance relevant to pneumatic filling situations under-predicted the effects. The effect of the vent duct is to some extent mitigated, in these tests, because the grid across the vent which protects the vent cover from wind forces means that the effective vent area is less than the cross-sectional area of the duct. Under favourable circumstances this means that the vent duct has less of an effect on explosion pressures than if the duct area and vent area were the same. The highest pressures in these tests occurred with ducts consisting of a sharp bend close to the vent followed by a 3 m of straight duct. Light-weight weather protection at the end of a duct can have an additional effect on the explosion pressure. Crown