The charged fraction of submicrometer and ultrafine particles generated during bench scale coal combustion and the subsequent penetration of particles through a cylindrical-wire electrostatic precipitator (ESP) in O(2)-CO(2) and O(2)-N(2) environments were measured. In all combustion environments, natural particle charging within the combustor was not adequate for high efficiency particle collection in the ESP; thus, corona generation was necessary for enhanced particle charging. With a positive applied potential, the corona inception voltage and voltage required to reach a given current level in the ESP in gas mixtures composed of O(2) and CO(2) were higher than those composed of O(2) and N(2), while similar voltages were needed for negative corona generation. In positive coronas, particle penetration through the ESP in O(2)-CO(2) environments was 1-2 orders of magnitude higher than in O(2)-N(2) environments. Little difference in particle penetration between O(2)-N(2) and O(2)-CO(2) was seen in negative coronas. (C) 2007 Elsevier Ltd. All rights reserved.