The report describes Phase I of a program during which a unique 3.7 million Btus/hr oil combustor was designed and built to develop NOx control techniques f or small boilers. The facility duplicates key aspects of oil flames of representative boilers in the 1 million to 1 billion Btu/hr range, and can recycle and inject any amount of flue gas or air at unconventional sites on the combustion boundary. The facility can also measure all flows (air, fuel, and flue gas), temperatures along the combustor, and NOx, CO, O2, and smoke emissions. Preliminary tests indicate that emissions from the combustor operating on No. 6 oil, are consistent with emissions from field-tested package boilers. In Phase two, the combustor will be used to screen many different applications of combustion modification techniques for controlling pollutant emissions. Phase three will include long-term testing of the optimum configurations.