The influence of distributor design, including orifice size, number and positioning, on the behaviour of a gas-fluidised granular bed has been studied experimentally. The use of Positron Emission Particle Tracking (PEPT) to non-invasively probe the system's three-dimensional dynamics has allowed the extent of (de)fluidisation and the homogeneity of particle distribution to be quantitatively characterised. While increasing the number of orifices demonstrates a dear, positive influence on both fluidisation quality and homogeneity, the data obtained suggest that the orifice size and positioning play a more complex role. (C) 2020 Published by Elsevier B.V.