The Sulfur hexafluoride reference article from the English Wikipedia on 24-Apr-2004
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Sulfur hexafluoride

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Sulfurhexafluoride (SF6) is a colorless, odorless, nontoxic, nonflammable, liquefied gas.

Sulfurhexafluoride is used as an insulator for circuit breakers, switch gear, and other electrical equipment. It is also emited during the aluminium smelting process.

SF6 has a GWP (global warming potential) 22,200 times that of CO2.