Combustion data for a wide range of coals were obtained in a 160 kW(th) NOx reduction test facility (NRTF). Parametric testing was undertaken under conditions of single-stage combustion, furnace air staging and natural gas reburning. From these tests, detailed information directly applicable to large utility furnaces on the effects of coal characteristics, excess air, stoichiometry and residence time on NOx, CO and unburnt loss is now available. The data show that there are considerable differences between coal types, but even coals of similar properties can display large variations in combustion performance. The differences between coals are reduced under advanced low-NOx combustion conditions. Confidence in the NRTF results is enhanced by comparison with large plant data; for NOx the NRTF gave good agreement with a large utility boiler in both absolute emission and coal effects.