Sulfur hexafluoride or sulphur hexafluoride (British spelling) is an inorganic compound with the formula SF6. It is a colorless, odorless, non-flammable, and non-toxic gas. SF 6 has an octahedral geometry, consisting of six fluorine atoms attached to a central sulfur atom. It is a hypervalent molecule.[citation needed] Typical for a nonpolar gas, SF 6 is poorly soluble in water but quite soluble in nonpolar organic solvents. It has a density of 6.12 g/L at sea level conditions, considerably higher than the density of air (1.225 g/L). It is generally stored and transported as a liquefied compressed gas.[8] SF 6 has 23, 500 times greater global warming potential (GWP) than CO2 as a greenhouse gas (over a 100-year time-frame) but exists in relatively minor concentrations in the atmosphere. Its concentration in Earth's troposphere reached 11.50 parts per trillion (ppt) in October 2023, rising at 0.37 ppt/year.[9] The increase since 1980 is driven in large part by the expanding electric power sector, including fugitive emissions from banks of SF 6 gas contained in its medium- and high-voltage switchgear. Uses in magnesium, aluminium, and electronics manufacturing also hastened atmospheric growth.[10] The 1997 Kyoto Protocol, which came into force in 2005, is supposed to limit emissions of this gas. In a somewhat nebulous way it has been included as part of the carbon emission trading scheme. In some countries this has led to the defunction of entire industries.[11]