The application of different characterization techniques to the study of coal fly ash formation and of its behaviour in particulate control devices is discussed. Particle Induced X-ray Emission (PIXE) and Proton Induced Gamma-ray Emission (PIGE) are used for bulk elemental analyses, while X-Ray Photoelectron and Auger Spectroscopies are used for surface elemental analyses. Structural characterization is carried out by powder X-Ray Diffraction and Raman Microfocus Spectroscopy. The effect of different collection efficiencies of electrostatic precipitators on emitted fly ash characteristics is addressed. Furthermore size fractionated fly ash is analyzed to investigate the mechanisms of particle growth.