A new fine particulate emissions measurement and characterization system was developed at the CANMET Energy Technology Centre (CETC). The computer controlled, ambient-simulating method is being used to determine source characteristic profiles of emissions from an oil-fired research boiler. Controlled source dilution of flue gas simulates realistic plume conditions that allow atmospheric condensation and accumulation of particulate matter. Isokinetic withdrawal of flue gas is followed by 20- to 40-fold dilution with pure air inside a Teflon(TM) coated tunnel. Subsequent sampling of PM2.5, PM10 and PMTotal fractions is done at specified sampling ports using appropriate inlet and filter pack arrangements. Gas phase acidic species are collected using annular denuders attached upstream of filter packs. Detailed characterization of particulate samples provides new source information on size distribution and chemical composition such as trace metal contents, organic and elemental carbons, and particle bound acids from oil combustion. The results available to date from this ongoing research program are presented. The new methodology provides reproducible source profile data for No. 4 residual fuel combustion. Size distribution results show that particles collected in all of the PM2.5, PM10, and PMTotal fractions fall within the expected size ranges. These studies indicate reliable pre-selection of particle sizes by the inlets and collection efficiency of the filter pack arrangements. The approximate particulate emission mass balance results as determined by gravimetric determination and by composite analysis of various particle bound components are in good agreement. Ongoing work focuses on field particulate emissions measurement from utility coal-fired boilers. (C) 2000 Minister of Natural Resources, Canada,