Physical Science, Measurement and Instrumentation, Management and Education, IEE Proceedings A

Sulphur hexafluoride (SF₆) is used as an insulating gas for electrical applications (gas-insulated substations, switchgear etc.). The gas is inert chemically and innocuous biologically. Electrical discharges (arcs, sparks, corona) in SF₆ can produce chemical decomposition of the gas. Analysis by mass spectroscopy at the Oak Ridge National Laboratory, Tennessee, USA, has found that discharge of electrical sparks in SF₆ can produce a wide variety of decomposition products depending on electrode composition, moisture content, presence of oxygen etc. The compounds SOF₂, SOF₄, SO₂F₂, SiF₄, SO₂, HF, SF₄ and S₂F₁₀ have been identified and quantified in laboratory samples of spark-decomposed SF₆. Toxicity information on most of these chemicals is sparse, but available data suggest some may have a strong, concentration-dependent biological toxicity. Analysis of the ability of these individual chemicals to cause cell lethality in cultured cell assays has allowed a toxicity ranking for these compounds, and an understanding of which compounds contribute most to cellular toxicity in the cell culture assays. Based on the authors´ own experiments and other observations, certain recommendations regarding worker safety in utility applications can be made.