The report gives results of testing three fuels in a small (732 kW) firetube package boiler to determine emissions of carbon monoxide (CO), nitrogen oxide (NO), particulate matter (PM), and total hydrocarbons (THCs). The tests were part of EPA's Environmental Technology Verificiation (ETV) program. The thermal efficiency of the boiler was also calculated for each fuel. Fuels tested were a standard No. 2 fuel oil, the same No. 2 fuel oil emulsified with 30 vol% water, and a fuel naphtha emulsified with 30 vol% water. Emissions and thermal efficiencies measured when using the emulsied fuels were compared with those of the non-emulsified fuel. NO emission concentrations decreased 15-34% for the emulsified No. 2 oil and 33-51% for the emulsified naphtha compared to the No. 2 oil. CO and THC emissions were < 8 ppm (at 3% O2) and PM emissions were < 5 mg/dscm for these fuels. Boiler efficiency was 2-3 percentage points lower for the emulsified fuels than for the non-emulsified fuel.