Hydrogen storage and adsorption studies in carbon materials have been of great concern in recent years. Hydrogen is thought to be an ideal energy source because of causing no pollutants or greenhouse gases during combustion unlike the fossil fuels. In this study, sorption characteristic of H-2 and N-2 gases in activated carbon having three different particle sizes were investigated in a temperature range of 303-473 K using a dynamic technique. The experimental procedure consist of introducing a pulse of H-2 and N-2 on the inlet of a column packed with activated carbon samples and measuring the concentration versus time response peak leaving the other end of the column. Adsorption equilibrium constants were evaluated using the moment analysis of the chromatographic peaks. At 473 K, the adsorption equilibrium constant for H-2 on activated carbon having 4.76-0.85 mm particle size (ACI) was found to be 7.92 x 10(-4), whereas it has value of 1.83 x 10(-3) m(3)/kg at 303 K. Heats of adsorption of H-2 and N-2 on ACI were determined as -4.8 and -11.6 kJ mol(-1), respectively. The values of heat of adsorption obtained indicate physical adsorption of H-2 and N-2 gases on the activated carbon samples used. (C) 2007 International Association for Hydrogen Energy. Published by Elsevier Ltd. All rights reserved.