Fly ashes from (i) coal and (ii) biomass combustion were studied for physicochem. properties (d., unburned C content, particle size distribution). The SiO2 content in the fly ash was 54-55% by mass. The alkali contents (Na2O + K2O + CaO) were 6.7% (i) and 6.9% (ii), resp. The results of the study aimed at developing the construction of an electrostatic precipitator, as well as the performance and selection of operating parameters in household applications.