Dry cleaning operations release cleaning solvent vapors to the atmosphere. While perchloroethylene (tetrachloroethylene) is the primary solvent used in dry cleaning operations, some stoddard solvent facilities may still exist. Emission rates are dependent upon the type of equipment used by the facility, emission controls, and the volume of cleaning performed. Equipment types are typically described as closed-loop, dry to dry, or transfer machines. Control devices may include refrigerated condensers, carbon adsorbers, separators, stills, filters, and/or diatomaceous earth.