Typical for anonpolar gas,SF 6 is poorlysoluble 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 thedensity of air (1.225 g/L). It is generally stored and transported as aliquefied compressed gas.[10]
SF 6 has 23,500 times greaterglobal warming potential (GWP) than CO2 as agreenhouse gas (over a 100-year time-frame) but exists in relatively minor concentrations in the atmosphere. Its concentration in Earth'stroposphere reached 12.06parts per trillion (ppt) in February 2025, rising at 0.4 ppt/year.[11] The increase since 1980 is driven in large part by the expanding electric power sector, includingfugitive emissions from banks ofSF 6 gas contained in its medium- and high-voltageswitchgear. Uses in magnesium, aluminium, and electronics manufacturing also hastened atmospheric growth.[12] The 1997Kyoto 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 thecarbon emission trading scheme. In some countries this has led to the defunction of entire industries.[13]
Sulfur hexafluoride on Earth exists primarily as asynthetic industrial gas, but has also been found to occur naturally.[14]
SF 6 can be prepared from the elements through exposure ofS 8 toF 2. This was the method used by the discoverersHenri Moissan andPaul Lebeau in 1901. Some other sulfur fluorides are cogenerated, but these are removed by heating the mixture todisproportionate anyS 2F 10 (which is highly toxic) and then scrubbing the product withNaOH to destroy remainingSF 4.[clarification needed]
Alternatively, usingbromine, sulfur hexafluoride can be synthesized from SF4 and CoF3 at lower temperatures (e.g. 100 °C), as follows:[15]
2 CoF3 + SF4 + [Br2] → SF6 + 2 CoF2 + [Br2]
There is virtually no reaction chemistry forSF 6. A main contribution to the inertness of SF6 is thesteric hindrance of the sulfur atom, whereas its heavier group 16 counterparts, such asSeF6 are more reactive than SF6 as a result of less steric hindrance.[16] It does not react with moltensodium below its boiling point,[17] but reactsexothermically withlithium. As a result of its inertness,SF 6 has an atmospheric lifetime of around 3200 years, and no significant environmental sinks other than the ocean.[18]
Gas-insulated electrical gear is also more resistant to the effects of pollution and climate, as well as being more reliable in long-term operation because of its controlled operating environment. Exposure to an arc chemically breaks downSF 6 though most of the decomposition products tend to quickly re-formSF 6, a process termed "self-healing".[21]Arcing orcorona can producedisulfur decafluoride (S 2F 10), a highlytoxic gas, with toxicity similar tophosgene.S 2F 10 was considered a potentialchemical warfare agent inWorld War II because it does not producelacrimation or skin irritation, thus providing little warning of exposure.
Alternatives toSF 6 as a dielectric gas include several fluoroketones.[22][23] Compact GIS technology that combines vacuum switching with clean air insulation has been introduced for a subset of applications up to 420 kV.[24]
SF 6 is used to provide atamponade or plug of a retinal hole inretinal detachment repair operations[25] in the form of a gas bubble. It is inert in thevitreous chamber.[26] The bubble initially doubles its volume in 36 hours due to oxygen and nitrogen entering it, before being absorbed in the blood in 10–14 days.[27]
SF 6 is used as a contrast agent forultrasound imaging. Sulfur hexafluoride microbubbles are administered in solution through injection into a peripheral vein. These microbubbles enhance the visibility of blood vessels to ultrasound. This application has been used to examine the vascularity of tumours.[28] It remains visible in the blood for 3 to 8 minutes, and is exhaled by the lungs.[29]
Sulfur hexafluoride was used as a non-toxic test gas in an experiment atSt John's Wood tube station inLondon, United Kingdom on 25 March 2007.[31] The gas was released throughout the station, and monitored as it drifted around. The purpose of the experiment, which had been announced earlier in March by theSecretary of State for TransportDouglas Alexander, was to investigate how toxic gas might spread throughoutLondon Underground stations and buildings during a terrorist attack.
Sulfur hexafluoride is also routinely used as a tracer gas in laboratory fume hood containment testing. The gas is used in the final stage ofASHRAE 110 fume hood qualification. A plume of gas is generated inside of the fume hood and a battery of tests are performed while a gas analyzer arranged outside of the hood samples for SF6 to verify the containment properties of the fume hood.
It has been used successfully as a transient tracer inoceanography to studydiapycnal mixing and air-sea gas exchange.[32] The concentration of sulfur hexafluoride in seawater (typically on the order of femtomoles per kilogram[33]) has been classified by the international oceanography community as a "level one" measurement, denoting the highest priority data for observing ocean changes.[34]
Themagnesium industry usesSF 6 as an inert "cover gas" to prevent oxidation duringcasting,[35] and other processes including smelting.[36] Once the largest user, consumption has declined greatly with capture and recycling.[12]
Insulated glazing windows have used it as a filler to improve their thermal and acoustic insulation performance.[37][38]
SF 6plasma is used in thesemiconductor industry as anetchant in processes such asdeep reactive-ion etching. A small fraction of theSF 6 breaks down in the plasma into sulfur and fluorine, with the fluorine ions performing a chemical reaction with silicon.[39]
Tires filled with it take longer to deflate fromdiffusion through rubber due to the larger molecule size.[37]
Nike likewise used it to obtain apatent and to fill the cushion bags in all of their "Air"-branded shoes from 1992 to 2006.[40] 277 tons was used during the peak in 1997.[37]
For entertainment purposes, when breathed,SF 6 causes the voice to become significantly deeper, due to its density being so much higher than air. This phenomenon is related to the more well-known effect of breathing low-densityhelium, which causes someone's voice to become much higher. Both of these effects should only be attempted with caution as these gases displaceoxygen that the lungs are attempting to extract from the air. Sulfur hexafluoride is also mildly anesthetic.[43][44]
For science demonstrations / magic as "invisible water" since a light foil boat can be floated in a tank, as will an air-filled balloon.
It is used for benchmark and calibration measurements in Associative and Dissociative Electron Attachment (DEA) experiments[45][46]
Sulfur hexafluoride (SF6) measured by the Advanced Global Atmospheric Gases Experiment (AGAGE) in the lower atmosphere (troposphere) at stations around the world. Abundances are given as pollution free monthly mean mole fractions inparts-per-trillion.
Abundance and growth rate ofSF 6 in Earth's troposphere (1978-2018).[12]
Atmospheric concentration of SF6 vs. similar man-made gases (right graph). Note the log scale.
Measurements of SF6 show that its global averagemixing ratio has increased from a steady base of about 54parts per quadrillion[14] prior to industrialization, to over 12 parts per trillion (ppt) as of February 2025, and is increasing by about 0.4 ppt (3.5%) per year.[11][49] Average global SF6 concentrations increased by about 7% per year during the 1980s and 1990s, mostly as the result of its use inmagnesium production, and by electrical utilities and electronics manufacturers. Given the small amounts of SF6 released compared tocarbon dioxide, its overall individual contribution to global warming is estimated to be less than 0.2%,[50] however the collective contribution of it and similar man-made halogenated gases has reached about 10% as of 2020.[51] Alternatives are being tested.[52][53]
In Europe,SF 6 falls under theF-Gas directive which bans or controls its use for several applications.[54] Since 1 January 2006,SF 6 is banned as a tracer gas and in all applications excepthigh-voltage switchgear.[55] It was reported in 2013 that a three-year effort by theUnited States Department of Energy to identify and fix leaks at its laboratories in the United States such as thePrinceton Plasma Physics Laboratory, where the gas is used as a high voltage insulator, had been productive, cutting annual leaks by 1,030 kilograms (2,280 pounds). This was done by comparing purchases with inventory, assuming the difference was leaked, then locating and fixing the leaks.[56]
Sulfur hexafluoride is a nontoxic gas, but by displacing oxygen in the lungs, it also carries the risk ofasphyxia if too much is inhaled.[57] Since it is more dense than air, a substantial quantity of gas, when released, will settle in low-lying areas and present a significant risk of asphyxiation if the area is entered. That is particularly relevant to its use as an insulator in electrical equipment since workers may be in trenches or pits below equipment containingSF 6.[58]
A man's voice is deepened in pitch through inhaling sulfur hexafluoride
As with all gases, the density ofSF 6 affects the resonance frequencies of the vocal tract, thus changing drastically the vocal sound qualities, ortimbre, of those who inhale it. It does not affect the vibrations of the vocal folds. The density of sulfur hexafluoride is relatively high at room temperature and pressure due to the gas's largemolar mass. Unlikehelium, which has a molar mass of about 4 g/mol and pitches the voice up,SF 6 has a molar mass of about 146 g/mol, and the speed of sound through the gas is about 134 m/s at room temperature, pitching the voice down. For comparison, the molar mass of air, which is about 80% nitrogen and 20% oxygen, is approximately 30 g/mol which leads to a speed of sound of 343 m/s.[59]
Sulfur hexafluoride has ananesthetic potency slightly lower thannitrous oxide;[60] it is classified as a mild anesthetic.[61]
^Assael MJ, Koini IA, Antoniadis KD, Huber ML, Abdulagatov IM, Perkins RA (2012). "Reference Correlation of the Thermal Conductivity of Sulfur Hexafluoride from the Triple Point to 1000 K and up to 150 MPa".Journal of Physical and Chemical Reference Data.41 (2): 023104–023104–9.Bibcode:2012JPCRD..41b3104A.doi:10.1063/1.4708620.ISSN0047-2689.S2CID18916699.
^Niemeyer L (1998), Christophorou LG, Olthoff JK (eds.), "SF6 Recycling in Electric Power Equipment",Gaseous Dielectrics VIII, Boston, MA: Springer US, pp. 431–442,doi:10.1007/978-1-4615-4899-7_58,ISBN978-1-4615-4899-7
^abcSimmonds, P. G., Rigby, M., Manning, A. J., Park, S., Stanley, K. M., McCulloch, A., Henne, S., Graziosi, F., Maione, M., and 19 others (2020) "The increasing atmospheric burden of the greenhouse gas sulfur hexafluoride (SF6)".Atmos. Chem. Phys.,20: 7271–7290.doi:10.5194/acp-20-7271-2020. Material was copied from this source, which is available under aCreative Commons Attribution 4.0 International License.
^Winter RW, Pugh JR, Cook PW (January 9–14, 2011).SF5Cl, SF4 and SF6: Their Bromine−facilitated Production & a New Preparation Method for SF5Br.20th Winter Fluorine Conference.
^Duward Shriver, Peter Atkins (2010).Inorganic Chemistry. W. H. Freeman. p. 409.ISBN978-1-4292-5255-3.
^Daniel A. Brinton, C. P. Wilkinson (2009).Retinal detachment: principles and practice. Oxford University Press. p. 183.ISBN978-0-19-971621-0.
^Gholam A. Peyman, M.D., Stephen A. Meffert, M.D., Mandi D. Conway (2007).Vitreoretinal Surgical Techniques. Informa Healthcare. p. 157.ISBN978-1-84184-626-2.{{cite book}}: CS1 maint: multiple names: authors list (link)
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^Lassau N, Chami L, Benatsou B, Peronneau P, Roche A (December 2007). "Dynamic contrast-enhanced ultrasonography (DCE-US) with quantification of tumor perfusion: a new diagnostic tool to evaluate the early effects of antiangiogenic treatment".Eur Radiol.17 (Suppl. 6):F89 –F98.doi:10.1007/s10406-007-0233-6.PMID18376462.S2CID42111848.
^J.L. Bullister and T. Tanhua, 2010. "Sampling and measurement of chlorofluorocarbons and sulfur hexafluoride in seawater". IOCCP Report No. 14.http://www.go-ship.org/HydroMan.html
^Stanley Holmes (September 24, 2006)."Nike Goes For The Green". Bloomberg Business Week Magazine. Archived fromthe original on June 3, 2013. RetrievedDecember 14, 2013.
^Hughes, T.G., Smith, R.B., Kiely, D.H. (1983). "Stored Chemical Energy Propulsion System for Underwater Applications".Journal of Energy.7 (2):128–133.Bibcode:1983JEner...7..128H.doi:10.2514/3.62644.
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^Adriani J (1962).The Chemistry and Physics of Anesthesia (2nd ed.). Illinois: Thomas Books. p. 319.ISBN978-0-398-00011-0.{{cite book}}:ISBN / Date incompatibility (help)
Maller VN, Naidu MS (1981).Advantages in High Voltage Insulation and Arc Interruption in SF6 and Vacuum. Oxford; New York: Pergamon Press.ISBN978-0-08-024726-7.OCLC7866855.
![Abundance and growth rate of SF 6 in Earth's troposphere (1978-2018).[12]](/mt/?noimg=&dark=on&url=http%3a%2f%2fen.wikipedia.org%2fwiki%2fFile%3aAGAGE_sulfur_hexafluroride_growth.png)
Material was copied from this source, which is available under aCreative Commons Attribution 4.0 International License.
