Editing Helium (section)

==Inhalation and safety==

===Effects===
Neutral helium at standard conditions is non-toxic, plays no biological role and is found in trace amounts in human blood.

{{Listen|right|filename=Helium article read with helium.ogg|title=Effect of helium on a human voice|description=The effect of helium on a human voice|format=[[Ogg]]}}
The [[speed of sound]] in helium is nearly three times the speed of sound in air. Because the [[fundamental frequency|natural resonance frequency]] of a gas-filled cavity is proportional to the speed of sound in the gas, when helium is inhaled, a corresponding increase occurs in the [[resonant frequency|resonant frequencies]] of the [[vocal tract]], which is the amplifier of vocal sound.<ref name="nbb" /><ref>{{Cite journal |last1=Ackerman |first1=M. J. |last2=Maitland |first2=G. |title=Calculation of the relative speed of sound in a gas mixture |journal=Undersea Biomed Res |volume=2 |issue=4 |pages=305–10 |date=1975 |pmid=1226588 |url=http://archive.rubicon-foundation.org/2738 |access-date=2008-08-09 |archive-url=https://web.archive.org/web/20110127113335/http://archive.rubicon-foundation.org/2738 |archive-date=2011-01-27 |url-status=usurped }}</ref> This increase in the resonant frequency of the amplifier (the vocal tract) gives increased amplification to the high-frequency components of the sound wave produced by the direct vibration of the vocal folds, compared to the case when the voice box is filled with air. When a person speaks after inhaling helium gas, the muscles that control the voice box still move in the same way as when the voice box is filled with air; therefore the [[fundamental frequency]] (sometimes called [[Pitch (music)|pitch]]) produced by direct vibration of the vocal folds does not change.<ref>{{cite web|date=14 July 2000|title=Why does helium make your voice squeaky?|url=http://www.straightdope.com/columns/read/1803/why-does-helium-make-your-voice-squeaky|url-status=live|archive-url=https://web.archive.org/web/20130324072558/http://www.straightdope.com/columns/read/1803/why-does-helium-make-your-voice-squeaky|archive-date=24 March 2013|access-date=2013-06-08}}</ref> However, the high-frequency-preferred amplification causes a change in [[timbre]] of the amplified sound, resulting in a reedy, duck-like vocal quality. The opposite effect, lowering resonant frequencies, can be obtained by inhaling a dense gas such as [[sulfur hexafluoride]] or [[xenon]].

===Hazards===
Inhaling helium can be dangerous if done to excess, since helium is a simple [[asphyxiant gas|asphyxiant]] and so displaces oxygen needed for normal respiration.<ref name="nbb" /><ref name="Grass">{{Cite journal|title = Suicidal asphyxiation with helium: Report of three cases Suizid mit Helium Gas: Bericht über drei Fälle|journal = Wiener Klinische Wochenschrift| volume = 119|issue =9–10|date = 2007|doi = 10.1007/s00508-007-0785-4|author = Grassberger, Martin|author2 = Krauskopf, Astrid |pages = 323–325 |language=de, en|pmid = 17571238|s2cid = 22894287}}</ref> Fatalities have been recorded, including a youth who suffocated in Vancouver in 2003 and two adults who suffocated in South Florida in 2006.<ref name="sptimes.com">{{cite news | title = 2 found dead under deflated balloon | url = http://www.sptimes.com/2006/06/03/Tampabay/2_found_dead_under_de.shtml | author = Montgomery B. | author2 = Hayes S. | date = 2006-06-03 | newspaper = Tampa Bay Times | access-date = 2013-12-29 | archive-url = https://web.archive.org/web/20131230235619/http://www.sptimes.com/2006/06/03/Tampabay/2_found_dead_under_de.shtml | archive-date = 2013-12-30 | url-status = live }}</ref><ref name="cbc.ca">{{cite news| url = http://www.cbc.ca/news/world/two-students-die-after-breathing-helium-1.623684| title = Two students die after breathing helium| publisher = CBC| date = 4 June 2006| access-date = 30 December 2013| archive-url = https://web.archive.org/web/20131231000044/http://www.cbc.ca/news/world/two-students-die-after-breathing-helium-1.623684| archive-date = 31 December 2013| url-status = live}}</ref> In 1998, an Australian girl from Victoria fell unconscious and temporarily [[cyanosis|turned blue]] after inhaling the entire contents of a party balloon.<ref name="balloonartists.com.au">{{cite web | url = http://balloonartists.com.au/helium-dangers.html | title = Helium inhalation – it's no laughing matter – Article courtesy of BOC Gases | publisher = Balloon Artists & Suppliers Association of Australasia Ltd | access-date = 2014-01-03 | archive-url = https://web.archive.org/web/20140114214605/http://www.balloonartists.com.au/helium-dangers.html | archive-date = 2014-01-14 | url-status = live }}</ref><ref name="lousballoons.com.au">{{cite web | url = http://www.lousballoons.com.au/dangers-of-helium.html | title = Dangers of Helium Inhalation | publisher = Lou's Balloons | url-status=dead | archive-url = https://web.archive.org/web/20140104032013/http://www.lousballoons.com.au/dangers-of-helium.html | archive-date = 2014-01-04 }}</ref><ref name="bouncetime.co.uk">{{cite web | url = http://www.bouncetime.co.uk/others_files/helium-gas-safety.htm | title = Helium Gas Safety & Data Sheet | publisher = bouncetime | access-date = 2014-01-03 | archive-url = https://web.archive.org/web/20150422003602/http://www.bouncetime.co.uk/others_files/helium-gas-safety.htm | archive-date = 2015-04-22 | url-status = live }}</ref>
Inhaling helium directly from pressurized cylinders or even balloon filling valves is extremely dangerous, as high flow rate and pressure can result in [[barotrauma]], fatally rupturing lung tissue.<ref name="Grass" /><ref name="slate">{{Cite news| author = Engber, Daniel| title = Stay Out of That Balloon!| publisher = Slate.com| date = 2006-06-13| url = http://www.slate.com/articles/news_and_politics/explainer/2006/06/stay_out_of_that_balloon.html| access-date = 2008-07-14| archive-url = https://web.archive.org/web/20111020154111/http://www.slate.com/articles/news_and_politics/explainer/2006/06/stay_out_of_that_balloon.html| archive-date = 2011-10-20| url-status = live}}</ref>

Death caused by helium is rare. The first media-recorded case was that of a 15-year-old girl from Texas who died in 1998 from helium inhalation at a friend's party; the exact type of helium death is unidentified.<ref name="balloonartists.com.au" /><ref name="lousballoons.com.au" /><ref name="bouncetime.co.uk" />

In the United States, only two fatalities were reported between 2000 and 2004, including a man who died in North Carolina of barotrauma in 2002.<ref name="sptimes.com" /><ref name="slate" /> A youth asphyxiated in Vancouver during 2003, and a 27-year-old man in Australia had an embolism after breathing from a cylinder in 2000.<ref name="sptimes.com" /> Since then, two adults asphyxiated in South Florida in 2006,<ref name="sptimes.com" /><ref name="cbc.ca" /><ref>{{cite journal | pmc = 1117755 | date = 2000 | last1 = Josefson | first1 = D. | title = Imitating Mickey Mouse can be dangerous | volume = 320 | issue = 7237 | pages = 732 | journal = BMJ: British Medical Journal | pmid=10720344}}</ref> and there were cases in 2009 and 2010, one of whom was a Californian youth who was found with a bag over his head, attached to a helium tank,<ref>{{cite news|url=http://www.ktla.com/news/landing/ktla-riverside-teen-helium,0,6589649.story |archive-url=https://web.archive.org/web/20120109032345/http://www.ktla.com/news/landing/ktla-riverside-teen-helium%2C0%2C6589649.story |archive-date=January 9, 2012 |title=Teen Dies After Inhaling Helium |date=January 6, 2010 |work=KTLA News |publisher=ktla.com |access-date=2010-11-19 |location=RIVERSIDE |url-status=dead }}</ref> and another teenager in Northern Ireland died of asphyxiation.<ref>{{cite news |url=https://www.bbc.co.uk/news/uk-northern-ireland-11795984 |title=Tributes to 'helium death' teenager from Newtownabbey |date=19 November 2010 |work=[[BBC Online]] |access-date=2010-11-19 |archive-url=https://web.archive.org/web/20101120085647/http://www.bbc.co.uk/news/uk-northern-ireland-11795984 |archive-date=20 November 2010 |url-status=live }}</ref> At [[Eagle Point, Oregon]] a teenage girl died in 2012 from barotrauma at a party.<ref>{{cite news|author=Mather, Kate|title=Parents of Eagle Point girl who died from inhaling helium hope to save others from same fate|url=http://www.oregonlive.com/pacific-northwest-news/index.ssf/2012/02/parents_of_eagle_point_girl_wh.html|work=The Oregonian|date=24 February 2012|access-date=2013-06-08|archive-url=https://web.archive.org/web/20131206170024/http://www.oregonlive.com/pacific-northwest-news/index.ssf/2012/02/parents_of_eagle_point_girl_wh.html|archive-date=6 December 2013|url-status=live}}</ref><ref name="huffingtonpost.com">{{cite news |last=Barnard |first=Jeff |title=Ashley Long, Oregon Teenager, Dies After Inhaling Helium at Wild Party (VIDEO) |url=http://www.huffingtonpost.com/2012/02/22/oregon-teenager-ashley-long_n_1294989.html |work=Huffington Post |date=22 February 2012 |access-date=30 December 2013 |archive-url=https://web.archive.org/web/20131231000509/http://www.huffingtonpost.com/2012/02/22/oregon-teenager-ashley-long_n_1294989.html |archive-date=31 December 2013 |url-status=live }}</ref><ref name="today.com">{{cite web |url=http://www.today.com/id/46487997 |title=Teen girl dies after inhaling helium at party |first=Jeff |last=Barnard |date=23 February 2012 |agency=AP |website=Today |access-date=2013-12-30 |url-status=dead |archive-url=https://web.archive.org/web/20131230233944/http://www.today.com/id/46487997 |archive-date=2013-12-30 }}</ref> A girl from Michigan died from hypoxia later in the year.<ref>''The Oxford Leader Newspaper'', Sherman Publications, Inc., December 3, 2012.</ref>

On February 4, 2015, it was revealed that, during the recording of their main TV show on January 28, a 12-year-old member (name withheld) of Japanese all-girl singing group [[3B Junior]] suffered from [[air embolism]], losing consciousness and falling into a [[coma]] as a result of air bubbles blocking the flow of blood to the brain after inhaling huge quantities of helium as part of a game. The incident was not made public until a week later.<ref>{{cite news|url=http://www.j-cast.com/2015/02/05227178.html|title=テレ朝事故で分かったヘリウム変声缶の危険性 意識を失うケースの大半が子ども|date=5 February 2015|access-date=2015-02-05|language=ja|archive-url=https://web.archive.org/web/20150205172253/http://www.j-cast.com/2015/02/05227178.html|archive-date=5 February 2015|url-status=live}}</ref><ref>{{cite magazine|url=https://time.com/3697523/jpop-3b-junior-helium-stunt/|title=J-Pop Teen Star Left in Coma After Inhaling Helium for TV Stunt|magazine=[[Time (magazine)|Time]]|date=5 February 2015|access-date=2015-02-06|first=Noah|last=Rayman|archive-url=https://web.archive.org/web/20150205195944/http://time.com/3697523/jpop-3b-junior-helium-stunt/|archive-date=5 February 2015|url-status=live}}</ref> The staff of [[TV Asahi]] held an emergency press conference to communicate that the member had been taken to the hospital and is showing signs of rehabilitation such as moving eyes and limbs, but her consciousness has not yet been sufficiently recovered. Police have launched an investigation due to a neglect of safety measures.<ref>{{cite news|url=http://www.sponichi.co.jp/entertainment/news/2015/02/04/kiji/K20150204009750570.html|title=アイドルが収録中に倒れ病院搬送 テレ朝、ヘリウムガス吸引|date=4 April 2015|access-date=2015-02-04|language=ja|archive-url=https://web.archive.org/web/20150204230036/http://www.sponichi.co.jp/entertainment/news/2015/02/04/kiji/K20150204009750570.html|archive-date=4 February 2015|url-status=live}}<br />{{cite news|url=http://www.sankei.com/affairs/news/150204/afr1502040032-n1.html|title=テレビ番組収録中、12歳アイドルが意識失い救急搬送 ヘリウムガスが原因か|date=4 February 2015|access-date=2015-02-04|language=ja|archive-url=https://web.archive.org/web/20150204230008/http://www.sankei.com/affairs/news/150204/afr1502040032-n1.html|archive-date=4 February 2015|url-status=live}}<br />{{cite news|url=http://www.hochi.co.jp/entertainment/20150204-OHT1T50098.html|title=テレ朝謝罪、12歳アイドルがヘリウム吸い救急搬送|date=4 February 2015|access-date=2015-02-04|language=ja|url-status=dead|archive-url=https://web.archive.org/web/20150204090914/http://www.hochi.co.jp/entertainment/20150204-OHT1T50098.html|archive-date=2015-02-04}}<br />{{cite news|url=http://www.tokyoreporter.com/2015/02/04/3b-junior-idol-in-coma-after-inhaling-helium-on-tv-asahi-program/|title=3b Junior idol in coma after inhaling helium on TV Asahi program|date=4 February 2015|access-date=2015-02-04|archive-url=https://web.archive.org/web/20150204230158/http://www.tokyoreporter.com/2015/02/04/3b-junior-idol-in-coma-after-inhaling-helium-on-tv-asahi-program/|archive-date=4 February 2015|url-status=live}}<br />{{cite news|url=http://www.tokyo-sports.co.jp/entame/entertainment/363851/|title=アイドル救急搬送騒動で制作会社が実績削除の不可解|date=4 February 2015|access-date=2015-02-04|language=ja|archive-url=https://web.archive.org/web/20150204124022/http://www.tokyo-sports.co.jp/entame/entertainment/363851/|archive-date=4 February 2015|url-status=live}}</ref><ref>{{cite news|url=https://www.bbc.com/news/entertainment-arts-31147038|title=Japanese child star in coma after helium stunt goes wrong|publisher=[[BBC]]|date=5 February 2015|access-date=2015-02-06|archive-url=https://web.archive.org/web/20150205195830/http://www.bbc.com/news/entertainment-arts-31147038|archive-date=5 February 2015|url-status=live}}</ref>

The safety issues for cryogenic helium are similar to those of [[liquid nitrogen]]; its extremely low temperatures can result in [[frostbite|cold burns]], and the liquid-to-gas expansion ratio can cause explosions if no pressure-relief devices are installed. Containers of helium gas at 5 to 10 K should be handled as if they contain liquid helium due to the rapid and significant [[thermal expansion]] that occurs when helium gas at less than 10 K is warmed to [[room temperature]].<ref name="LANL.gov" />

At high pressures (more than about 20&nbsp;atm or two&nbsp;[[MPa]]), a mixture of helium and oxygen ([[heliox]]) can lead to [[high-pressure nervous syndrome]], a sort of reverse-anesthetic effect; adding a small amount of nitrogen to the mixture can alleviate the problem.<!--<ref>{{cite web| last = Campbell| first = Ernest S.| title = High Pressure Nervous Syndrome| work = Physics and Problems With Gases|date = 2008-05-13| url = http://www.scuba-doc.com/HPNS.html| access-date = 2008-07-16}}</ref>--><ref>{{Cite journal|author=Rostain J.C.|author2=Lemaire C.|author3=Gardette-Chauffour M.C.|author4=Doucet J.|author5=Naquet R.|title=Estimation of human susceptibility to the high-pressure nervous syndrome |journal=J Appl Physiol |volume=54 |issue=4 |pages=1063–70 |date=1983|pmid=6853282|doi=10.1152/jappl.1983.54.4.1063}}</ref><ref name="HungerBennett" />