What not to do at a party!
Chemicly neutral helium that is inhaled in standard conditions is non-toxic, plays no biological role and is found in trace amounts in human blood. Don't inhale or ingest helium, it may prove deadly if done to an excess.
The speed of sound in helium is nearly three times the speed of sound in air. Because the fundamental frequency of a gas-filled cavity is proportional to the speed of sound in the gas, when helium is inhaled there is a corresponding increase in the resonant frequencies of the vocal tract. The fundamental frequency (sometimes called musical pitch) does not change, since this is produced by direct vibration of the vocal folds, which is unchanged. However, the higher resonant frequencies cause a change in timbre, resulting in a high-pitched, reedy, duck-like vocal quality. The opposite effect occurs when lowering resonant frequencies which can be obtained by inhaling a dense gas such as sulfur hexafluoride or xenon. Both of them can suffocate you to.
Inhaling helium can be dangerous if done to excess since helium is a simple asphyxiate gas, and so displaces oxygen needed for normal respiration. Blackouts, physical trauma from falling during a black out and embolisms been known to have occurred as well.
Fatalities have been recorded, including a youth who suffocated in Vancouver in 2003 and two adults who suffocated in South Florida in 2006. In 1998, an Australian girl (her age is not known) from Victoria fell unconscious and temporarily turned blue after inhaling the entire contents of a party balloon. Breathing pure helium continuously causes death by asphyxiation within minutes.
This fact is utilized in the design of suicide bags. Several authors have also reported various cases of 'suicide by helium' over the years.
Inhaling helium directly from pressurized cylinders is extremely dangerous and has even killed some people, as the high flow rate can result in barotrauma in the thought and lungs, fatally rupturing lung tissue from barotrauma from inhaling the gas from a pressurized cylinder at a party.
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.
Globally Between 1993 and 2007, only 18 people were recorded as having died from inhaling it, but it increased to 27 between 2007 and 2014. In 1998, an Australian school girl (her age is not known) from Victoria fell unconscious and temporarily turned blue after inhaling the entire contents of a party balloon. The other identified fatalities included a 2002 case report from a Japanese medical journal described as an incident when a drunken Japanese adolescent stuck his head into an advertising balloon and asphyxiated earlier that year. A man in Australia had an embolism after breathing from a cylinder in 2000, and a youth asphyxiated in Vancouver during 2003.
In the United States only two fatalities were reported between 2000 and 2004, including a 48 year-old software consultant who died in N. Carolina of barotrauma in 2002. The son of a prominent Tampa jeweler and young woman from Lutz were found dead after climbing inside a by then deflated helium inflated promotional balloon used to advertise condominiums at Lake View, Calusa Trace in 2006. 10-year-old New Jersey boy collapsed and blacked out in at a 2006 birthday party in after sucking helium from a balloon. There were cases in 2009 and 2010, one a Californian youth who was found with a bag over his head, attached to a helium tank, and later at Eagle Point, Oregon a teenage girl died in the November of 2012
A 12 year old girl from Clarkston, Michigan died from hypoxia later in the year. A 44 year old nurse from Millbourne, Delaware County, Pennsylvania died a day earlier in 2012 while inhalation it from a bag she put over her head. A 10 year old boy from Bethlehem, Pennsylvania, passes out and almost died after inhaling helium from a balloon at a party on December 6, 2012.
3 have died in the UK. On the 19th of November, 2010, another teenager in Northern Ireland died of asphyxiation. A 16 year old Manchester boy died in 2013 and a 23 year old Student from Manchester in 2015.
Only 1 known case has occurred in Azerbaijan, when a 13 year old girl died at a 2009 Baku party.
Reported, but medically not confirmed deaths occurred in 2002 at Chicago- 2 youths, Florida- 2 youths, Norfolk (U.K.)- 1 youth and 1 kid, Vancouver- 1 youth and Dresden (Germany)- 1 kid.
The safety issues for cryogenic helium are similar to those of liquid nitrogen ; it’s 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.
At high pressures (more than about 20 atm or two MPa), a mixture of helium and oxygen (heliox) can lead to high-pressure nervous syndrome , a sort of reverse-aesthetic effect; adding a small amount of nitrogen to the mixture can alleviate the problem.