This paper presents a theoretical and experimental study of the transient adsorption characteristics of vertical packed porous bed. The theoretical model describes the effect of independent parameters (time and vertical distance through the bed) on the vertical gradient of adsorbable fluid in the bed. A simplified analytical solution, for specific operating conditions, is also presented. In the experimental study, porous granules of burned clay are applied as a desiccant carrier in the fixed bed. The granules of the packed bed are impregnated with liquid calcium chloride solution to form the porous adsorbing surface. The isothermal adsorption of water vapour from atmospheric air using the prepared bed is experimentally studied. Transient values of the mass of adsorbed water vapour, solution concentration and vapour pressure through the bed layers are evaluated from the experimental measurements. The model output, which show the effect of dimensionless relative time (Tr) on the potential ratio (C-C*)/(C-C-0*), is compared with the experimental results and good agreement is found. (C) 2002 Elsevier Science Ltd. All rights reserved.