In an isothermal fixed bed absorption system for constant mlet flowrate of mert gas and concentrations of two adsorbates the more strongly adsorbed component wdl chsplace the weaker one and affect Its breakthrough characteristics A small scale techmque was used to study this phenomenon for the adsorptIon of water vapour and carbon choxlde on 4A type synthetic zeohtes with helmm as the earner gas Smgle adsorbate eqmhbna and rate data determmed with the binary nuxtures were then used to calculate the results for the ternary one Partial dfierentml equations were derived to descnbe the mass transfer of each adsorbate based on pore diffusion m the adsorbent as a major rate controllmg mechamsm With a simphfied binary Langmulr eqmhbnum to descnbe the effect of water on the adsorption of carbon dioxide, and assummg that the effective pore dtiuslon coefficient of one adsorbate was not affected by the presence of the other, accurate predIctions of the concentration transients were obtained Four zones are formed m the bed with the ternary nuxture resultmg from the desorption of carbon choxlde by water, the concentrations of the former nsmg above the mlet value An enhanced rate of adsorbed phase transport of water was found, adchtlonal to that expected from macropore dtiuslon, suggesting that surface or capdlary flow of the adsorbate occurred