Experiments have been carried out to study the effect of secondary air supply rate on the combustion of volatile as in a controlled-air incinerator. The secondary air supply was varied at flow rates of 0.56, 1.026, 1.73Nm(3)/min. The waste in this study was categorized into three types: namely those containing low, medium and high combustible matter. The significant results of the experimental investigation shown that increasing secondary air supply rate reduces the chamber temperature in both chambers and strong effect on CO reduction for waste with high combustible content. NO formation increases slightly as secondary air supply increases and SO2 formation depends on the sulfur content in the waste and insensitive to secondary air for the range of flow rate tested. Copyright © 2005 John Wiley & Sons, Ltd.