Sulfur hexafluoride (SF6) is a relatively nontoxic gas used in a number of applications for its inert qualities. The dielectric and other physical and chemical properties related to its lack of reactivity have led to the extensive use of SF6 as an insulating medium in switching equipment (e.g., circuit breakers) by electric utilities. While SF6 is inert during normal use, when electrical discharges occur within SF6-filled equipment, toxic byproducts can be produced that pose a threat to health of workers who come into contact with them. This paper discusses these byproducts and how they are formed, and also summarizes relevant health and safety concerns, as well as handling, detection, and safety procedures and guidelines. U.S. EPA produced this background paper as a service to its partners in the SF6 Emission Reduction Partnership for Electric Power Systems. This is a voluntary program in which partner companies agree to reduce SF6 emissions through technically and economically feasible actions. SF6 is a potent and persistent greenhouse gas, with a global warming potential approximately 24,000 times greater than carbon dioxide over a 100-year time horizon and a residency in the atmosphere of more than 3,000 years. Although SF6 is critical to the reliable distribution of electricity, program participants recognize the importance of careful management and responsible use.