The use of helium for leak detection has varied widely from year to year, having accounted for approximately 3 to 6 percent of helium consumption in the United States from 1970 to 2006.

There are several approaches to reduce the usage of helium for leak detection. One alternative gas would be hydrogen, whose molecule is only slightly larger than a helium atom but has the disadvantage of flammability. One solution is to mix 4 percent hydrogen with nitrogen to keep it below the hazardous range. However this mixture is much less sensitive than pure hydrogen or helium. Another option with limited applicability is to use closed-loop systems for leak detection. None of these techniques will fully replace helium. For this reason, helium will probably continue to dominate leak detection for the foreseeable future and will have only limited responsiveness to price.

Breathing Mixtures

Several gas combinations containing helium are widely used as breathing mixtures. Although many alternative gas mixtures containing hydrogen or inert gases other than helium have been tried, they are not likely to see wide application or serve as substitutes for mixtures containing helium. The main gases that have been used are Heliox, Trimix, and Heliair, which are mixtures of helium and oxygen, helium with nitrogen and oxygen, and helium and air. Heliox has been used for medical applications since the 1930s to alleviate the symptoms of upper airway obstruction, and its medical use in recent years has expanded. Trimix and Heliair are strictly for nonrecreational use in military, scientific, commercial, and advanced technical diving.

Substitutes also include neon, whose greater density results in less absorption by body tissues than helium or nitrogen. A mixture of 75 percent neon and 25 percent helium has been used, as well. Neon does not seem to have any narcotic effects but is only very slowly released from body tissues, causing long decompression times. Argon is a highly narcotic gas (significantly more so than nitrogen) and because it is dense, it makes breathing difficult on very deep dives. Breathing mixtures containing helium constitute 2 to 3 percent of the use of helium. The growth in this application is not known nor is there any obvious route to helium recovery.



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