Current estimates indicate that up to 160 short tons (146 Mg) of mercury (Hg) is consumed by the chlor-alkali industry each year. Very little quantitative information is currently available, however, on the actual Hg losses from these facilities. The Hg cell building roof vent is considered to be the most significant potential emission point in chlor-alkali plants, especially when the cells are opened for maintenance. Because of their potential importance, chlor-alkali plants have been identified as needing more accurate measurements of Hg emissions. To obtain a better understanding of the fate of Hg within their manufacturing process, the Olin Corporation voluntarily agreed to cooperate with the U.S. Environmental Protection Agency in a comprehensive study of the Hg emissions from their Augusta, GA, facility, in collaboration with other members of the Chlorine Institute representing the active chlor-alkali plants in the United States.