The paper discusses the fuel oil portion of an evaluation, utilizing a multistaged combustion burner designed for in-furnace NOx control and high combustion efficiency, for high nitrogen content fuel and waste incineration application in a 0.6 MW package boiler simulator. A low NOx precombustion chamber burner has been reduced in size by about a factor of two (from 600 to 250 ms first-stage residence time) and coupled with (1) air staging, resulting in a three-stage configuration, and (2) natural gas fuel staging, yielding up to four stoichiometric zones. Natural gas, doped with ammonia to yield a 5.8% fuel nitrogen content, and distillate fuel oil, doped with pyridine to yield a 2% fuel nitrogen content, were used to simulate high nitrogen content fuel/waste mixtures. The multistaged burner reduced NO emissions by 85% from emission levels from a conventional unstaged burner mounted on a commercial package boiler. A minimum NO emission level of 110 ppm was achieved in the fuel oil tests, from a level of 765 ppm for conventional firing. This is compared with a 160 ppm minimum NO level achieved in gaseous fuel tests, from an uncontrolled level of 1000 ppm. (Copyright (c) 1988, APCA.)