Direct measurements of the gas phase composition within a laboratory-scale N 2 pressure swing adsorption (PSA) bed operating at cyclic steady state were made. The objective of this work was to study the shape and movement of the mass transfer zone (MTZ) within a kinetics-based PSA system. The results of this study confirmed model predictions that the MTZ spans a large portion of the bed under favourable operating conditions. The shape of the MTZ during the adsorption step changes from concave upwards to ’s’ to concave downwards with time. Maximum air recovery tends to occur if the feed step is stopped just after the MTZ turns to concave downwards. The experimental results also revealed an important and beneficial role the pressure equalization step plays in the establishment of the solid phase MTZ.