Mist or aerosol explosions present a serious hazard to process industries. Heat transfer fluids are widely used in the chemical process industry, are flammable above their flash points, and can cause aerosol explosions. Though the possibility of aerosol explosions has been widely documented, knowledge about their explosive potential is limited. Studying the formation of such aerosols by emulating leaks in process equipment will help define a source term for aerosol dispersions and aid in characterizing their explosion hazards. Current research conducted at the Mary Kay O'Connor Process Safety Center involves the non-intrusive measurement of heat transfer fluid aerosol sprays using a Malvern Diffraction Particle Analyzer. A predictive correlation relating aerosol droplet diameters to bulk liquid pressures, temperatures, thermal and fluid properties, leak sizes, and ambient conditions is presented. This correlation can be used to predict the conditions under which leaks will result in the formation of aerosols and ultimately help in estimating the explosion hazards of heat transfer fluid aerosols. The goal is to provide information that will help improve safety in process industries. (C) 2003 Elsevier Science Ltd. All rights reserved.