The pure substance of sulfur hexafluoride is a colorless, odorless, non-toxic gas. It is the heaviest of all the known gases, with a density of 6.14 grams per liter at room temperature. Sulfur hexafluoride is also very unreactive, and does not react with most other substances. It is used in a variety of applications, including as an insulating gas in electrical equipment, as a refrigerant, and as a tracer gas for leak detection.