The results of experimental tests conducted on a conical fluidised bed combustor (FBC), firing mixed sawdust of some Thai woods, are discussed. The concentration profiles for major gaseous emissions (CO, NOx and CO2), as well as the temperature and O-2 profiles along the combustor height, were obtained for various operating conditions (fuel feed rate and excess air) for three "fixed" bed heights (20, 30 and 40 cm). The influence of fuel quality (through varying the fuel's moisture content) on the formation of gaseous emissions was also studied. Both CO and NOx axial profiles were found to have an extreme (maximum) in the active combustion zone. The effects of FBC load and excess air, as well as fuel moisture, on the COmax were found to be very strong. The NOx,max was less affected by the combustion conditions, approaching 1.5-3 times the NOx values at the combustor outlet. The influence of the sand's bed height on the rate of gaseous emissions was found to be minor. The dependencies of the CO and NOx emissions (i.e. concentrations in the waste flue gas) on the FBC operating conditions are shown for different values of fuel's moisture content. (C) 2003 Elsevier Science Ltd. All rights reserved.