Helium is a colorless, odorless, nonreative inert gas which is compressed to high pressures. It acts as a simple asphyxiant by displacing air.
It is used as an inert gas shield in arc welding, as a lifting gas for lighter-than-air aircraft, as a gaseous cooling medium in nuclear reactors, to provide a protective atmosphere for growing germanium and silicon crystals for transistors, to provide a protective atmosphere in the production of such reactive metals as titanium and zirconium, to fill cold-weather fluorescent lamps, to trace leaks in refridgeration and other closed systems, and to fill neutron and gas thermometers. It is used cryogenic research such as for superconductivity. In mixtures with oxygen, it has medical applications. Radioactive mixtures of helium with krypton are available to users licensed by the Nuclear Regulatory Commission. Liquid helium is also gaining wide use for cooling superconductive magnets used in magnetic resonance imaging.
The primary source of helium is from natural gas wells. It is obtained by a liquefaction and stripping operation. A new process for recovering helium utilized the diffusion of helium through quartz. Helium is also obtained in small quantities from the air by liquefaction, rectifications, and selective adsorption on charcoal at low temperatures.
Gaseous helium is commonly stored in high pressure cylinders, hydril tubes, or tube trailers. Liquid helium is commonly stored at the consumer site in cryogenic liquid cylinders and specially designed insulated tanks. To minimize helium transfer losses, the shipping container for liquid helium is normally used for storage.