Applications Helium is used for many purposes that require some of its unique properties, such as its low boiling point, low density, low solubility, high thermal conductivity, or inertness. Helium is commercially available in either liquid or gaseous form. As a liquid, it can be supplied in small containers called Dewars which hold up to 1,000 liters of helium, or in large ISO containers which have nominal capacities as large as 11,000 gallons (41,637 liters). In gaseous form, small quantities of helium are supplied in high pressure cylinders holding up to 300 standard cubic feet, while large quantities of high pressure gas are supplied in tube trailers which have capacities of up to 180,000 standard cubic feet. Because of its low density and incombustibility, helium is the gas of choice to fill airships such as the Goodyear blimp. Airships, balloons and rocketry Because it is lighter than air, airships and balloons are inflated with helium for lift. While hydrogen gas is approximately 7% more buoyant, helium has the advantage of being non-flammable.[26] In rocketry, helium is used as an ullage medium to displace fuel and oxidizers in storage tanks and to condense hydrogen and oxygen to make rocket fuel. It is also used to purge fuel and oxidizer from ground support equipment prior to launch and to pre-cool liquid hydrogen in space vehicles. For example, the Saturn V booster used in the Apollo program needed about 13 million cubic feet (370,000 m³) of helium to launch.[39] Commercial and recreational Helium alone is less dense than atmospheric air, so it will change the timbre (not pitch[78]) of a person's voice when inhaled. However, inhaling it from a typical commercial source, such as that used to fill balloons, can be dangerous due to the risk of asphyxiation from lack of oxygen, and the number of contaminants that may be present. These could include trace amounts of other gases, in addition to aerosolized lubricating oil. For its low solubility in nervous tissue, helium mixtures such as trimix, heliox and heliair are used for deep diving to reduce the effects of narcosis.[79][80] At depths below 150 metres (490 ft) small amounts of hydrogen are added to a helium-oxygen mixture to counter the effects of high pressure nervous syndrome.[81] At these depths the low density of helium is found to considerably reduce the effort of breathing.[82] Helium-neon lasers have various applications, including barcode readers.[2] Industrial For its inertness and high thermal conductivity, neutron transparency, and because it does not form radioactive isotopes under reactor conditions, helium is used as a heat-transfer medium in some gas-cooled nuclear reactors.[83] Helium is used as a shielding gas in arc welding processes on materials that are contaminated easily by air.[2] Helium is used as a protective gas in growing silicon and germanium crystals, in titanium and zirconium production, and in gas chromatography,[39] because it is inert. Because of its inertness, thermally and calorically perfect nature, high speed of sound, and high value of the heat capacity ratio, it is also useful in supersonic wind tunnels[84] and impulse facilities[85]. Because it diffuses through solids at three times the rate of air, helium is used as a tracer gas to detect leaks in high-vacuum equipment and high-pressure containers.[83] Helium, mixed with a heavier gas such as xenon, is useful for thermoacoustic refrigeration due to the resulting high heat capacity ratio and low Prandtl number.[86] The inertness of helium has environmental advantages over conventional refrigeration systems which contribute to ozone depletion or global warming.[87] Liquid helium is used to cool the superconducting magnets in modern MRI scanners. Scientific The use of helium reduces the distorting effects of temperature variations in the space between lenses in some telescopes, due to its extremely low index of refraction.[23] This method is especially used in solar telescopes where a vacuum tight telescope tube would be too heavy.[88][89] The age of rocks and minerals that contain uranium and thorium can be estimated by measuring the level of helium with a process known as helium dating.[2][23] Liquid helium is used to cool certain metals to the extremely low temperatures required for superconductivity, such as in superconducting magnets for magnetic resonance imaging. The Large Hadron Collider at CERN uses 96 tonnes of liquid helium to maintain the temperature at 1.9 Kelvin.[90] Helium at low temperatures is also used in cryogenics. http://en.wikipedia.org/wiki/Helium#Applications

Talking funny

I have heard of them being used inside shower curtain rings to make them lighter. A travelling 'shower curtain ring' salesman did that once.