What is Helium?
Helium is a chemical element and a colorless, odorless, tasteless, inert gas. It has the smallest atomic
radius of any element and the second lowest atomic weight. It is lighter than air.
Most people know that helium is used as a lifting gas in blimps and party balloons, but they can't name another way in
which it is used. The number one use of helium is as a cooling gas for magnetic resonance imaging (MRI) machines
used in medical facilities. Other important uses of helium include: a
protective gas for welding, an inert gas for controlled atmosphere manufacturing, a fugitive gas used for leak
detection, and a low viscosity gas for pressurized breathing mixtures.
Where Does Helium Come From?
Very little helium is present in Earth's atmosphere. It is such a light element that Earth's gravity can not
hold it. When present at Earth's surface, unconfined helium immediately begins rising until it escapes the planet.
That's why party balloons rise!
The helium that is produced commercially is obtained from the ground. Some natural gas fields have enough helium
mingled with the gas that it can be extracted at an economical cost. A few fields in the United States contain over
7% helium by volume. Companies that drill for natural gas in these areas produce the natural gas, process it and
remove the helium as a byproduct.
Why is Helium in Some Natural Gas?
Most of the helium that is removed from natural gas is thought to form from radioactive decay of uranium and
thorium in granitoid rocks of Earth's continental crust. As a very light gas it is buoyant and seeks to move upward as
soon as it forms. The richest helium accumulations are found where three conditions exist: 1) granitoid basement
rocks are rich in uranium and thorium; 2) the basement rocks are fractured and faulted to provide escape paths for
the helium; and, 3) porous sedimentary rocks above the basement faults are capped
by an impermeable seal of halite or anhydrite.  When all three of these conditions are met, helium might accumulate in the porous sedimentary rock layer.
Helium has the smallest atomic radius of any element, about 0.2 nanometers. So, when it forms and starts moving
upward it can fit through very small pore spaces within the rocks. Halite and anhydrite are the only sedimentary rocks that can block the upward
migration of helium atoms. Shales that have their pore spaces plugged with abundant organic materials (kerogen) sometimes serve as
a less effective barrier.
Where is Natural Gas Rich in Helium?
Most unprocessed natural gas contains at least trace amounts of helium. Very few natural gas fields contain enough to justify a helium recovery process.
A natural gas source must contain at least 0.3% helium to be considered as a potential helium source.
In 2010, all of the natural gas processed for helium in the United States came from fields in Colorado, Kansas, Oklahoma, Texas,
Utah and Wyoming as shown on the map at right. The Hugoton Field in Oklahoma, Kansas and Texas; the Panoma Field in Kansas; the
Keyes Field in Oklahoma; the Panhandle West and Cliffside Fields in Texas and the Riley Ridge Field in Wyoming account for
most of the helium production in the United States. 
World Helium Resources
Billion Cubic Meters
The values above are estimated helium resources from the USGS Mineral Commodity Summary 
During 2010, the United States produced 128 million cubic meters of helium. Of that amount, 53 million cubic meters of helium
was extracted from natural gas and 75 million cubic meters was withdrawn from the National Helium Reserve. Other countries with known
production amounts were: Algeria (18 mcm), Qatar (13 mcm), Russia (6 mcm), and Poland (3 mcm). Canada and China produced small but
unreported amounts of helium. 
Properties and Uses of Helium
Helium has a number of properties that make it exceptionally well-suited for certain uses.
In some of these uses, helium is the best possible gas to use and in a few there is no adequate substitute for helium. Several uses of helium along with the properties that make it suitable for the use are described below.
Magnetic Resonance Imaging
The number one use of helium is in the magnetic resonance imaging machines used in medical facilities
to assess injuries and diagnose illness. These machines utilize a magnetic field that is produced by
a superconducting magnet. These magnets generate an enormous amount of heat. Liquid helium is the
cooling substance of choice for regulating the temperature of these magnets. Because helium has the
second lowest specific heat of any gas and the lowest boiling/melting point of any element there is no
foreseen substitute for helium in this very important use.
Helium has the second lowest atomic weight of any element. Only hydrogen has a lower atomic weight.
As a lighter-than-air gas, helium has been used as a "lifting gas" for airships and balloons. Blimps,
dirigibles, zeppelins, anti-aircraft balloons, weather balloons and other lighter-than-air craft have all
used helium as a lifting gas. It is much safer than hydrogen because it is not flammable. This was the most important
category of helium use until the end of World War II. Much lower amounts of
helium are now used as a lifting gas.
Helium has the lowest melting and boiling point of any gas. It melts and boils at temperatures close
to absolute zero. Because it remains a gas at very low temperatures, it can be used as a purging gas
for fuel tanks and fuel delivery systems that are filled with very cold liquids such as liquid hydrogen
and liquid oxygen. Because it is inert and has a low freezing temperature, it can displace these fuels safely without freezing. Large amounts of
helium are used by NASA and the Department of Defense for purging rocket propulsion systems.
Controlled Atmosphere Manufacturing
Helium is an inert gas. The only gas with a lower reactivity is neon. This low reactivity makes
helium a valuable gas to use in manufacturing and repair processes when an inert atmosphere is
required. Helium also has the second lowest density of any gas along with a very high thermal
conductivity. These properties of helium gas make it the atmosphere of choice for many metallurgical
processes, growing perfect crystals in chemical vapors, manufacturing optical fibers and other uses.
Helium has a very low viscosity, a high diffusion coefficient and the smallest atom of any element.
These characteristics make helium very hard to contain. If a system has a leak, helium will escape.
Helium gas is therefore used to test high vacuum systems, fuel systems and other containments for leaks.
Helium and other inert gases are used to prepare breathing mixtures for deep-water diving and
medical treatments. Helium is used here because it is inert, has a very low viscosity and is easier to breathe under pressure
than any other gas.
Helium is used as a protective atmosphere when welding. An inert gas atmosphere protects hot
metals from oxidation and other reactions that might occur rapidly at high temperatures.
Helium: A Nonrenewable Resource
Helium is a gas that is only found where a coincidence of unlikely
situations occur. Although it is continually being produced by radioactive mineral decay
in Earth's crust, its rate of natural production and accumulation is so slow that it must be considered a
National Helium Reserve
In 1925 the United States established the National Helium Reserve to serve as a strategic
supply of helium for use in airships and other defense purposes. Although the use of helium
for these purposes declined after World War II, new defense uses began. Helium was used as
a purging gas when refueling rocket engines and as a coolant in nuclear weapons programs.
In 1995, Congress decided that the National Helium Reserve was not essential and initiated a
program to sell the helium as part of the Helium Privatization Act of 1996.  Since then
up to 1/2 of the world's helium demand has been met through sales from the National Helium
Reserve and in some years more helium is exported out of the United States to other countries
than is consumed domestically. 
Many people believe that the dumping of National Helium Reserve stock into the market has depressed
the price of helium so much that it is being used as a cheap substitute for argon and other gases that
have a much less limited supply. Because commercial helium production has not been rewarded or
heavily utilized, the market will be undersupplied when National Helium Reserve sales are discontinued.
When that occurs the free market price could shoot up by an order of magnitude as inadequate commercial
capacity is stressed.  
Contributor: Hobart King
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|Most people have heard of helium being used as a lifting gas for weather balloons, blimps and party balloons. These are very minor uses of helium. The use that consumes more helium than any other is cooling the magnets in MRI (magnetic resonance imaging) machines in medical facilities. Goodyear blimp photo by Derek Jensen.
|Map showing the natural gas fields that serve as important sources of helium in the United States. The natural gas produced from these fields contains between 0.3% to over 7% helium. The helium is removed from the gas for commercial sale. Image by Geology.com using location data from the United States Geological Survey. |
|Deposit model for helium-bearing natural gas fields in the United States. Helium is produced by the decay of uranium and thorium in granitoid basement rocks. The liberated helium is buoyant and moves toward the surface in porosity associated with basement faults. The helium then moves upward through porous sedimentary cover until it is trapped with natural gas under beds of anhydrite or salt. Image by Geology.com.|
|Relative amounts of helium consumed by various uses in the United States during 2011. Graph by Geology.com using data from USGS.
|The number one use of helium is cooling the magnets in the MRI (magnetic resonance imaging) machines used to diagnose disease and injury in medical facilities.
|Helium is used by NASA and the Department of Defense to purge liquid oxygen and liquid hydrogen from fuel tanks and fuel delivery systems of rocket engines. Helium is inert and has a freezing temperature that is so low that it remains a gas through the purging process. A flow of helium into these systems has even been used during emergencies to extinguish fires. Image by NASA.
|Helium is used to prepare breathing gas mixtures for deep water diving. Helium is inert and has a low viscosity under pressure which allows easier breathing. Image by NOAA.
 Helium in New Mexico: Ronald F. Broadhead, New Mexico Geology, New Mexico Bureau of Geology and Mineral Resources, New Mexico Institute of Mining and Technology, November, 2005.
 Helium 2010: Joseph B. Peterson and Peter J. Madrid, Minerals Yearbook, United States Geological Survey, January 2012.
 Helium 2012: Peter J. Madrid, Mineral Commodity Summary, United States Geological Survey, January 2012.
 Selling the Nation's Helium Reserve: Committee on Understanding the Impact of Selling the Helium Reserve, National Research Council, The National Academies Press, 2010.
 Helium Sell-Off Risks Future Supply: Michael Banks, PhysicsWorld.com, website article, January 2010.
 Price Shocks Waiting as US Abandons Helium Business: John Timmer, website article on ArsTechnica.com, July, 2010.