In this work, separation of hydrogen from carbon monoxide by a polyimide hollow fiber membrane module was investigated. Polyimide showed high selectivity for hydrogen relative to carbon monoxide at different operational conditions. Effects of temperature, pressure and stage-cut on permeability of gases and membrane selectivity were experimentally studied. The experiments were carried out employing mixtures containing: 0, 10, 25, 40 and 50% carbon monoxide. Feed temperatures and pressures were varied between 20 and 80 degrees C and 5-9 bar, respectively. Pure gas permeances through the membrane were found to be nearly constant at different pressures. Also, the results confirmed the plasticization effect of carbon monoxide on the membrane and showed reduction of hydrogen permeance in mixed gas experiments due to competitive sorption and concentration polarization effects. Also, membrane area for a specific separation was calculated using a new developed model. The optimum condition which results in minimum required area for the membrane can be determined in this way. (c) 2008 Elsevier B.V. All rights reserved.