The report gives methods and results of an environmental assessment test program at an industrial site. The aim of the program was to measure multimedia emissions changes as a result of applying NOx controls. Emissions of trace elements, organic materials, sulfur species, SO2, NOx, CO, and particulate metter were measured. These emissions, under normal and controlled (for NOx) operating conditions, were compared. Source operating data were also analyzed so that changes in operating parameters and efficiency could be assessed. This unit is a spreader-stoker coal-fired boiler rated at 38 kg/s (300,000 lb/hr) of steam. The fuel tested was low-sulfur coal. High overfire air firing (constant overall air flow) was used for NOx control. These measures reduced NOx by about 10% from baseline. Increased overfire air levels also improved boiler efficiency. These tests lasted about 5 hours; long-term operation under test conditions was not addressed in this program. Test results suggest that applying combustion modification NOx controls increased particulate and organic emissions.