To fully assess the suitability of nanoporous carbon (NPC) membranes for industrial applications such as carbon capture, it is necessary to understand the impact of impurities commonly present in the feed streams upon the membrane performance. In this work, the effect on the performance of a NPC membrane upon exposure to condensable impurities typically found in natural gas (e.g. water, hexane and toluene) and non-condensable impurities typically found in synthesis gas (e.g. H(2)S and CO) has been determined in laboratory experiments. Small reductions in the permeance (less than 30%) and minimal reductions in selectivity have been observed, with the greatest impact at 35 degrees C and less impact at 100 degrees C. The performance of a NPC membrane upon exposure to real synthesis gas produced from air-blown coal gasification, as part of the Mulgrave Capture Project, has also been determined. The combined higher concentrations of impurities in these pilot plant experiments resulted in a greater impact on performance at 100 degrees C with a reduction in CO(2) permeance of around 40% and in CO(2)/N(2) selectivity of around 25%. However, these relatively limited reductions in membrane performance suggest that such carbon membranes still offer some promise for pre-combustion applications. (C) 2011 Elsevier BM. All rights reserved.