Some industrial dust-handling plant is designed so that, should an explosion occur, the over-pressures can be totally contained. Such plant needs to be designed to withstand at least 10 bar overpressure. This may suffice for single compact vessels but experience indicates that in interconnected plant, explosion overpressures can be substantially increased. This effect is due to a process known as pressure-piling, There is no adequate guidance on how to take the effects of this process into account. This paper describes a project in which the behaviour of dust explosions in systems of linked enclosed vessels has been studied. Explosions of coal dust and toner dust have been produced in a number of linked systems using vessels ranging in size from 2 to 20 m(3) and connected by 5 m lengths of pipe with diameters of 0.15 m, 0.25 m and 0.5 m. Pressure changes that occur when a dust explosion is ignited in one of the vessels and the flame transmits into the other have been measured. Pressure enhancement due to pressure-piling effects occurs in some systems, and pressures approaching 20 bar have been measured. The pipe diameter, vessel volumes and the volume ratio are important variables. These results are discussed and a simple method for the calculation of explosion pressure enhancement effects is described. Comparisons are made between the model predictions of the maximum explosion pressure and experimental measurements. The experiments have shown that, in some circumstances, there is a low probability of an explosion propagating along the pipe to produce an explosion in the second vessel. It appears that although the flame travels through the pipe and a jet flame enters the second vessel, it does not act as an effective ignition source. The wider the pipe diameter, the higher the frequency of an explosion in the second vessel.