Removal of H2S to ultra-low concentrations using an asymmetric hollow, fibre membrane module was studied from gas streams containing 17.9-1159 ppm H2S. The absorption medium used was 2 M sodium carbonate (NaCO3) aqueous solution. A porous polyvinylidene fluoride (PVDF) asymmetric hollow fibre membrane was used as the barrier between the liquid and gas phases. The effect of various operating conditions on H2S outlet concentration and mass transfer coefficient was examined. The operating conditions examined included the feed gas concentration, the gas velocity (resident time), the liquid velocity, and the gas pressure. The PVDF hollow, fibre membrane module was found to be very efficient in purification of gas streams containing soluble toxic gases. With the feed concentrations of 17.9-1159 ppm H2S complete removal of H2S can be reached at very short resistance time (<0.1 s) and low liquid/gas flow ratio. The mass transfer coefficient strongly depends on the gas phase pressure and gas flow rate. (C) 2002 Elsevier Science B.V. All rights reserved.