NOx and SOx emissions of air-staged combustion were investigated in a 1 MW tangentially-fired furnace combusting a high sulfur self-retention coal. Two variables including the air stoichiometric ratio of primary combustion zone and the relative location of over-fire air (OFA) injection ports were studied. These results suggest that NOx reduction efficiency monotonically increases with increasing the relative location of OFA injection ports, and the lowest NOx emissions are achieved when the air stoichiometric ratio of primary combustion zone is 0.85. In the meantime, SOx emissions can be effectively reduced when the air stoichiometric ratio of primary combustion zone is 0.85 or 0.95, and SOx emissions monotonically decrease with increasing the relative location of OFA injection ports. (C) 2007 Elsevier Ltd. All rights reserved.