Abstract: Apparatus and method for removing particulates and corrosive gases from a gas stream includes the serial use of a condensing wet electrostatic precipitator section for removing smaller particulates, in the submicron range, in conjunction with a vertically aligned preliminary scrubber section which removes larger particulates, in the micron range, and corrosive gases, in an integrated unit in which the temperature and moisture conditions in the gas stream are controlled for assuring effective and efficient operation of the condensing wet electrostatic precipitator section. Discharge electrodes of the electrostatic precipitator are supported by insulators which are protected against deleterious deposits of particulates by discharge electrode elements and collector electrode elements placed between the gas stream and the insulators.