This paper discusses a portion of a research program recently completed for the U.S.Environmental Protection Agency and the Federal Energy Administration (1) to systematicallyevaluate the effectiveness of additives for increasing boiler efficiency and reducingcombustion-generated air pollutant emissions from an oil-fired continuous combustion system.This program was unique in that an extensive and well-documented program was conducted toevaluate a large number of proprietary additives and pure compounds under controlled conditionsin a single unit--a commercial 50-hp (500 kW) Scotch firetube boiler firing residual oil. This work is an extension of the work of G. B. Martin, et al., who systematically evaluated about300 additives for reducing emissions from a distillate oil-fired residential burner (2).