Thus far, the elemental characterization of particles in energy conversion process gases and emissions has conventionally either been performed offline or information on the particle size has not been available. Such processes include combustion in engines or thermal treatments of renewable and fossil fuels for heat and power generation. One established physical aerosol measurement instrument is the scanning mobility particle sizer (SMPS), providing size distribution and concentration of gas-borne particles online, with temporal resolutions of a few minutes or even less. However, a far greater wealth of information can be gained by combining the opportunities of the SMPS with those of an inductively coupled plasma mass spectrometer (ICPMS), which enables the determination of the elemental composition of an introduced sample with low detection limits and a wide dynamic measuring range, and those of a rotating disk diluter (RDD), used as a sample introduction interface, making the setup independent of a defined aerosol source flow. We have recently presented such an instrumental setup, which is used now for online measurements on particulate sodium, chlorine, potassium, and copper, in aerosols emitted by differently impregnated wood samples, heated in a thermogravimetric analyzer (TGA). The TGA allows controlling the temperature, oxygen content, and gas flows in the furnace and is used for generating model aerosols to study the influence of different fuel treatments on the emissions during the combustion process. The ability of RDD-SMPS-ICPMS to discriminate between several elements contained in specific particle size classes between 13 and 340 nm at different times in the aerosol emitted by a thermal process is demonstrated.