Helium

Helium (symbol He, atomic number 2) is a chemical element and the lightest of the noble gases. At standard conditions it is a colorless, odorless, monatomic gas with extremely low chemical reactivity. Its atoms have two protons and usually two neutrons in the nucleus, with two electrons filling the innermost shell. Helium has the lowest boiling point of any element and stays liquid at normal pressure down to absolute zero, which makes it central to low-temperature physics.

Helium is the second most abundant element in the universe, formed mainly in the Big Bang and in stellar fusion, yet it is rare on Earth. Terrestrial helium comes from the radioactive decay of heavy elements and is collected mainly as a by-product of natural gas. Its uses include cooling the superconducting magnets of MRI scanners, semiconductor manufacturing, leak detection, and research instruments. Because it cannot be readily replaced in many of these roles, supply disruptions have significant downstream effects.

This entry covers helium's atomic structure and physical properties, its discovery, its limited chemistry, the superfluid behavior of its two stable isotopes, its origin in the cosmos and in the Earth's crust, its extraction and distribution, its applications, supply and shortages, and its safety and research frontiers.

Atomic structure and basic properties

A helium atom has two protons in its atomic-nucleus and two electrons, which together give the ground-state configuration 1s². The first shell holds at most two electrons under the pauli-exclusion-principle, so that shell is completely filled. A closed shell gives the atom almost no tendency to gain or lose electrons. This accounts for helium's chemical inertness and for its first ionization-energy of about 2372 kJ/mol, the highest of any element. Its electron affinity is effectively zero, so it does not readily accept an extra electron either. Helium sits at the head of Group 18 in the periodic-table, among the noble gases.

Helium has two stable isotopes. The common isotope, helium-4, has two neutrons alongside its two protons, giving a mass-number of 4. The rarer helium-3 has only one neutron. Helium-4 makes up almost all natural helium, roughly 99.999 percent, while helium-3 accounts for about 0.0001 percent. The mass difference is small, but the two isotopes obey different quantum statistics. Helium-4 nuclei have a total spin of zero and behave as bosons, so many atoms can share the same quantum state. Helium-3 has half-integer spin and is a fermion, so it obeys the Pauli principle in the same way as electrons. This difference becomes decisive at low temperature, where the two isotopes condense into superfluid phases at very different temperatures.

In bulk, helium is a colorless, odorless, tasteless, monatomic gas that is not known to be toxic under ordinary conditions. Its density is about 0.18 g/L at room temperature, which makes it the second-lightest gas after hydrogen and roughly one-seventh as dense as air. Its boiling point is 4.22 K (−268.93 °C) at normal pressure, the lowest of any element, and its critical temperature is only about 5.2 K. Liquid helium-4 has a density of about 125 g/L at its boiling point, roughly one-eighth that of water. The gas also conducts heat well for its kind, with a thermal-conductivity of about 0.15 W/(m·K) at room temperature, second among gases only to hydrogen. These properties follow from the very weak attraction between helium atoms. The forces are of the van der Waals type, and they are too feeble to hold the atoms in a fixed arrangement at ordinary pressure.

The most unusual property, the failure to freeze at absolute-zero, comes from quantum-mechanics. A confined particle always retains some zero-point-energy, and this quantity grows as the particle becomes lighter and more tightly confined. For helium, the zero-point motion of each atom is larger than the depth of the weak attractive well between atoms. The atoms therefore cannot settle into a crystal lattice at zero pressure, and the substance stays liquid at temperature approaching 0 K. Solidifying helium requires external pressure of roughly 25 bar at about 1 K. Helium-3, which is lighter in its nuclear mass, shows even stronger quantum behavior and likewise remains liquid. Because the liquid is governed by quantum effects rather than classical thermal motion, it is classed as a quantum fluid. Its properties differ sharply from those of an ideal-gas or a conventional cryogenic liquid, and this difference underlies the superfluid behavior discussed in a later section.

Discovery and naming

Helium was first recognized in the Sun, not on Earth. On 18 August 1868, the French astronomer Pierre Janssen travelled to Guntur in India to watch a total solar eclipse, and through a prism he saw a bright yellow line in the light from the Sun's chromosphere. The first evidence of helium was obtained on August 18th, 1868 by French astronomer Jules Janssen. While in Guntur, India, Janssen observed a solar eclipse through a prism. The line did not match any known element. Because it lay close to the sodium D lines, Janssen first assumed it came from sodium, but he later reproduced the line without an eclipse and confirmed that it was not sodium or any other known element.

Some weeks later, the English astronomer Joseph Norman Lockyer found the same yellow line working from London. On October 20 of that same year, astronomer Joseph Norman Lockyer independently observed the same yellow line in the solar chromosphere without needing an eclipse. Lockyer concluded that the line came from an unknown element in the Sun, and he proposed a name derived from the Greek word for the Sun, hēlios. Accounts differ on who should be credited with the name. Only Lockyer proposed that the line was due to a new element, which he named after the Sun. Other accounts state that he and a compatriot, chemist Edward Frankland, dubbed the element helium. The two astronomers' letters reached the French Academy of Sciences at nearly the same time, and there was no priority dispute, with both scientists receiving joint credit in France.

The identification was not immediately accepted. In the following years, there remained much doubt (and even mockery) over Lockyer's discovery. Frankland later publicly renounced his involvement in the work. Dmitri Mendeleev also left the element out of the periodic table he published in 1869. Among the scientists who did not accept that such an element could exist on Earth was Dmitri Mendeleev, who left it out of his iconic periodic table published in 1869.

The terrestrial discovery came in 1895. The Scottish chemist William Ramsay was looking for argon when he treated the uranium-bearing mineral cleveite with acid. While searching for argon, Scottish chemist Sir William Ramsay managed to isolate helium by treating a sample of cleveite with mineral acids. After treating the element with sulfuric acid, he noticed the same D3 absorption line. Ramsey sent samples of the gas to Sir William Crookes and Sir Norman Lockyer, who verified that it was helium. In the same year, chemists Per Teodor Cleve and Abraham Langlet in Uppsala, Sweden, were able to accurately determine its atomic weight. An earlier report had come from Luigi Palmieri, who in 1882 detected helium on Earth when analyzing lava from Mount Vesuvius after it erupted in that year. The 1895 work is generally treated as the isolation of the element on Earth.

The discovery was closely tied to radioactivity. Cleveite contains uranium, and helium released from the mineral linked the element to radioactive processes. Later in the same research tradition, Ernest Rutherford and Thomas Royds showed in 1908 that alpha particles are helium nuclei, which connected helium directly to alpha decay and placed it within nuclear physics. The history therefore runs in two stages: first, spectroscopy of the Sun identified the element through its light, and then chemistry and radioactivity research in the laboratory isolated it and explained its origin on Earth. Each stage depended on the other, and the combination is one reason the discovery is unusual in the history of science.

Chemical properties and compounds

Helium's chemistry follows from its electron structure. Researchers attribute its inertness to a closed-shell electronic configuration, together with zero electron affinity and a ionization energy that is the highest of any element, about 24.59 eV. As a result, helium is not known to form thermodynamically stable compounds under ordinary conditions, apart from a few inclusion compounds. The solid species that contain helium at ordinary pressure are van der Waals compounds such as NeHe2, which are held together only by weak van der Waals forces rather than by chemical bonds.

Ions and high-pressure compounds

The best-known helium-containing molecular species is the ion $\mathrm{HeH}^+$. Its importance lies in the early universe: neutral helium atoms formed the Universe's first molecular bond in the helium hydride ion, through radiative association with protons. In the laboratory, the ion was identified much earlier, discovered as long ago as 1925. Its charge distribution is lopsided, since the electron density in the ion is higher around the helium nucleus than the hydrogen, and this asymmetry is part of why its spectrum is easier to characterize than that of the related H₂⁺ ion.

Under extreme pressure, helium can be made to bond. A computational search predicted a stable compound of sodium and helium at 300 GPa in 2015. Experiments in a diamond anvil cell then produced the compound Na₂He, which is stable at pressures above 113 GPa. The reported structure is an electride, in which electrons that function as anions sit within a crystal built from positively charged cores. The presence of helium makes the material insulating, causing strong electron localization. The same study also predicted Na₂HeO, which should exist with a similar structure at pressures above 15 GPa, though it had not been prepared at the time.

Helium inside fullerene cages

Helium atoms can also be placed inside hollow carbon cages without forming bonds to them. Early work used collisions: in early mass spectrometry experiments, collisions of accelerated C60 or C70 ions with helium gas trapped a single helium atom inside the cage. Forcing helium in under high temperature and pressure was far less efficient, with about 0.1% insertion reported for noble gases in C60. Saunders and coworkers reported ³He@C60 in 1994, but the encapsulation level of the helium atom was quite low, at 0.15–0.4%.

Later, the so-called molecular surgery approach raised the yield. In this method, the cage is opened, helium is inserted, and the cage is closed again, reaching occupation levels of 30%. Further enrichment has produced a sample of ⁴He@C60 with 95% helium encapsulation. Spectroscopic work shows that the enclosed atom is not simply isolated: weak interactions between the inner helium and the outer fullerene cage were demonstrated by experimental and computational investigations. The cage's electronic structure also affects the helium nucleus. In the hexa-anion, the shielding of the encapsulated ³He is rationalized by the presence of a long-range shielding cone along the entire cage due to its spherical aromatic character. Even two helium atoms can be enclosed, since He2@C60 has been synthesized, with [He@C60] to [He2@C60] ratios of 200 to 1.

Inertness and practical use

Helium's low reactivity has a practical side. Because it rarely takes part in chemical reactions, it can be used as a carrier gas in analytical separations and as a protective atmosphere in semiconductor processing, where it does not alter the material being treated. The contrast with the Na₂He and $\mathrm{HeH}^+$ results shows that this inertness is a property of helium under ordinary conditions, and that it can change under extreme pressure or after ionization.

Low-temperature physics and superfluidity

Liquefaction in 1908

Helium was the last common gas to be liquefied, because its critical temperature lies only a few kelvin above absolute zero. On 10 July 1908, in his laboratory at Leiden, Heike Kamerlingh Onnes produced liquid helium for the first time. He precooled the apparatus with liquid hydrogen, which itself was made from liquid air, and the resulting liquid boiled at 4.2 K. By expanding the gas through the Joule–Thomson effect, he later pushed the temperature down to about 0.9 K, the lowest reached on Earth at that time. Keeping the sample pure was one of the main difficulties, and his laboratory was for years the only one able to make liquid helium. The access to temperatures in this range made possible the superconductivity experiments that Onnes began shortly afterwards, which is why the 1908 result is usually treated as a foundation of low-temperature physics as a whole.

Superfluidity of helium-4

Helium-4 has a boiling point of 4.2 K at atmospheric pressure, and its behavior changes sharply at the lambda point near 2.17 K. At that temperature the heat capacity shows a discontinuity and the liquid's density changes its trend, because part of the liquid enters a superfluid phase with zero viscosity. Onnes had already noted an unexplained density maximum near 2 K in the 1920s, but the superfluid state itself was only identified in experiments in 1938. Superfluid helium-4 creeps through very narrow channels with almost no resistance, climbs the walls of its container and can escape over the rim. Its heat transport is also unusual: heat moves through the superfluid as a wave, a phenomenon called second sound, rather than by ordinary conduction. Lev Landau explained much of this with a two-fluid model in which the liquid behaves as a mixture of a normal component and a superfluid component, and later work by Richard Feynman extended his theory.

Superfluidity of helium-3

Helium-3 has one fewer neutron than helium-4, which makes its atoms fermions rather than bosons, and fermions obey the Pauli exclusion principle and cannot all occupy the same state. The superfluid transition in helium-3 therefore requires the atoms to pair up, in a manner loosely analogous to the electron pairs in conventional superconductors. In the early 1970s David Lee, Douglas Osheroff and Robert Richardson at Cornell University found that liquid helium-3 becomes superfluid at temperatures of about 2.7 mK, and that below roughly 3 mK it passes through several distinct superfluid phases. These phases are magnetic and anisotropic, a combination that gives macroscopic quantum behavior unlike anything seen in helium-4. The discovery earned the three physicists the 1996 Nobel Prize in Physics. Theoretical understanding of the phases was developed soon afterward, and the helium-3 superfluid is now regarded as one of the most thoroughly understood condensed-matter systems.

Links to Bose–Einstein physics and quantum fluids

Helium-4 atoms are bosons, and the superfluid transition is generally connected to Bose–Einstein statistics and to the idea of a Bose–Einstein condensate. Interactions between atoms in liquid helium-4 are strong, so only a fraction of the atoms occupy the lowest quantum state, and the liquid is far from the ideal-gas picture. For this reason helium-4 has been a testing ground for condensate theory. The superfluid phases of helium-3 are also described as a particular kind of condensate, in which the paired atoms behave collectively as bosons. Studies of these quantum liquids have informed theories of other systems, including the hydrodynamics of ordered media and models of superconductivity, and the Cornell group's later work has been cited in connection with superconductivity and with the physics of the early universe.

Helium in the universe

Helium is the second most abundant element in the cosmos, and most of it was made in the first minutes after the Big Bang. This primordial helium formed during Big Bang nucleosynthesis, which took place roughly three to fifteen minutes after the event. The neutron-to-proton ratio at that stage was set by weak interactions, so the predicted helium yield depends mainly on how fast those reactions proceed. Current predictions give a helium-4 mass fraction of about 0.247, and cosmic microwave background measurements, which constrain the density of baryons, agree closely with this figure (see cosmic microwave background). By mass, helium-4 makes up about a quarter of ordinary matter, but because each helium nucleus contains four nucleons, fewer than one nucleus in twelve is helium-4.

Stars add to this inventory. In their cores, stars fuse hydrogen into helium through nuclear fusion, and this process supplies most of the energy they radiate during their main-sequence lives. Helium produced in stars is returned to the interstellar medium when stars shed their outer layers or explode, so the helium content of galaxies rises gradually over cosmic time. Later stages of stellar evolution go further: when a star's core becomes hot and dense enough, helium nuclei fuse into carbon and oxygen, through a sequence known as the triple-alpha process. Heavier elements are then built by successive fusion steps, with the most massive stars and supernovae producing many of the elements heavier than iron. In practical terms, the stellar contribution to helium is smaller than the primordial one, but it is the reason observed helium abundances can exceed the primordial value.

Helium was first detected in the Sun rather than on Earth. On 18 August 1868, during a total solar eclipse visible from Guntur in India, spectroscopy revealed a bright yellow line at about 587.5 nm in the spectrum of the solar prominences and chromosphere that did not match any known element. Pierre Janssen recorded it during the eclipse, and Norman Lockyer observed the same line independently in England that autumn. Janssen also showed that the line could be studied without an eclipse, by adjusting the instrument at the solar limb. Lockyer and the chemist Edward Frankland then proposed that the line came from a new element, which they named after the Greek word for the Sun. The detection is often described as the solar corona's contribution, but the spectra that revealed helium came from the chromosphere and prominences, not the corona.

Measurements of helium abundance serve as tests of theory. Spectroscopic studies of ionized gas clouds in nearby galaxies, and absorption features in intergalactic gas seen against distant quasars, provide independent estimates of the primordial helium fraction. These estimates must be extrapolated to zero metallicity, meaning the correction for helium produced by stars, and systematic uncertainties in this extrapolation currently dominate the error budget. Because the predicted primordial helium abundance depends on the number of neutrino species and on the baryon density, the observed value places limits on early-universe physics as well as on models of stellar evolution.

Natural occurrence on Earth

Trace presence in the atmosphere

Helium is only a trace component of air. Measurements made in 1981 by isotope dilution mass spectrometry gave a helium content of 5.222 + or - 0.017 ppm by volume, which agrees closely with a value first estimated from 1930s measurements. The concentration is so low that recovering helium from air is uneconomical. Converting atmospheric helium to high-purity grade requires 30 kJ per mole, and for that reason air is not an economical long-term helium source.

The gas is lost to space continuously. Helium atoms are light enough that, when heated, a share of them in the upper atmosphere reach the escape velocity of Earth. This thermal (Jeans) escape is the main loss mechanism for helium, a process described in more detail in atmospheric escape. The steady concentration in air therefore reflects a balance between helium seeping up from the crust and helium leaking out at the top of the atmosphere.

Crustal origin: alpha decay over geological time

Almost all terrestrial helium is radiogenic. It forms when heavy radionuclides in the crust emit alpha particles. The main contributors are the decay chains of uranium-238, uranium-235 and thorium-232, and each chain produces a different number of helium-4 atoms per parent atom; one atom of 238U produces 8 atoms of 4He, one atom of 235U produces 7 atoms of 4He, and one atom of 232Th produces 6 atoms of 4He. An alpha particle is a helium nucleus, and once it picks up two electrons it becomes a neutral helium atom. The rate is very slow. A crustal budget estimate gives about 8.0 × 10^12 cm^3 of 4He per year produced by uranium and thorium decay, compared with about 2.2 × 10^12 cm^3 of 4He released from the mantle at mid-ocean ridges.

The timescale is the main reason helium is scarce. The parent isotopes have half-lives of billions of years, so it takes millions of years to accumulate enough helium to fill a large reservoir. Helium that is not trapped soon after formation keeps migrating, so the reservoirs that exist today are the product of long periods of generation and slow transport.

Natural gas as the concentrating medium

Helium becomes economically significant mainly where it has been concentrated in natural gas. Helium content in gas deposits is normally quite low, but can range from 0.01% to 7%. The commercial cutoff is not fixed. One review of Chinese gas fields states that commercial helium can be obtained from reservoirs with helium contents higher than 500–1000 ppm, while an industry source puts the practical threshold at 0.3%. These figures differ partly because recovery costs depend on the scale and location of the field.

Concentration varies widely even within one basin. In the Four Corners area of the Colorado Plateau, helium concentrations range from 0.01% to 7.9%, along with varying amounts of hydrocarbons, nitrogen and carbon dioxide. In the Hetianhe gas field of the Tarim Basin, the helium concentration in the field ranges from 0.27% to 0.42%. Rare high-concentration finds also occur. A 2024 drilling program reported helium concentrations up to 14.5%, a figure the company itself described as the highest the industry has recorded in North America. Commentary on U.S. data indicates that only about 1 in 6 natural gas reservoirs in the U.S. has helium levels higher than 0.3%.

Some high-helium reservoirs cannot be explained by decay within the reservoir alone. The Four Corners study found that the volume of rock required to have produced helium in the reservoir is significantly larger than the current reservoir volume immediately beneath the field, which points to helium being introduced from outside the reservoir.

Geological controls on recovery

Whether helium can actually be recovered depends on how it moves and where it is held. Helium generated in basement rock migrates upward through the formations and is trapped by impermeable barriers. Rock permeability, the presence of effective seals, and the composition of the accompanying gas therefore control both how much helium collects and whether it can be produced. Helium tends to accompany a suitable carrier gas, which is one reason it is found mostly in hydrocarbon reservoirs. Generation is strongest where basement rocks are rich in uranium and thorium. Granite is a typical example, and the high concentrations of helium can be expected where there is a lot of uranium and thorium in the basement rock. Because helium is produced slowly and migrates readily, the age of the source rocks and reservoirs matters as well. In the Hetianhe field, for instance, the productive layers are of Ordovician and Carboniferous age, and the ancient age of these reservoirs means that the generated helium flux is not negligible even though present-day uranium and thorium levels are low.

Extraction, purification, and storage

Nearly all commercial helium is recovered from natural gas, where it is present only in small amounts. Gas fields typically hold helium at low concentrations of 0.2 % to 4 %, so producers must process very large volumes of gas to obtain useful quantities. Helium is chemically inert and does not get removed in ordinary gas processing. As a result it can accumulate in the processing steps, and recycle and purge streams can carry up to 2% or more by volume.

The main separation method is cryogenic distillation, which exploits the fact that helium stays gaseous at temperatures where other components condense. A typical plant first removes water, carbon dioxide and hydrogen sulfide, then separates the natural gas liquids at moderately low temperatures, and finally cools the stream until the hydrocarbons and nitrogen liquefy while helium remains a gas. A crude helium product separation step employing cryogenic temperatures yields a stream that is then upgraded further. The result, known as crude helium, usually contains about 50-70% helium and 50-30% nitrogen. Reaching the purity required by most markets, roughly 99.995 percent, requires an additional purification stage. This can combine partial condensation with adsorption to generate a pure helium stream containing over 99% helium.

Helium is also obtained as a by-product of other gas-processing operations. In liquefied natural gas production and nitrogen rejection, methane is condensed out and the lighter helium is easily recovered as a gas. Where such processing is absent, extraction is more costly. Cryogenic distillation has good economies of scale but is cost- and energy intensive, which is why membrane and adsorption-based alternatives have been studied.

Purified helium is then either liquefied or compressed. Liquefaction is the route for bulk supply, since helium boils at about 4.2 K and must be held in insulated cryogenic containers. For smaller users, gas is kept in high-pressure cylinders. Recovery equipment sold to laboratories, for example, compresses gas to up to 400 PSIG (27.58 bar) for medium-pressure systems and to much higher pressures for high-pressure options, and a single medium-pressure cylinder can hold ~16 liquid liters of helium.

Helium's very low molecular mass lets it diffuse through small gaps and seals, so storage and transfer systems must be sealed and leak-tested. Losses raise the cost of every transfer, which is one reason why transport is planned around containers that minimize boil-off.

Recovery and recycling are now standard practice in laboratories and hospitals that operate magnets and cryostats. A typical arrangement cycles helium first to an Atmospheric Helium Recovery Bag, after which the helium is compressed using a Recovery Compressor, the moved to Storage Cylinders, and finally purified before it returns to a liquefier. Recovery efficiency depends on the setup. One vendor's figures give roughly 70% for direct recovery, about 95% for medium-pressure systems and about 99% for high-pressure systems, and a university facility reports that it recover[s] 90% of the helium used by its NMR magnets and cryostat. Vendors promote recycling as a hedge: they describe it as a way to insulate against helium price fluctuations and supply shortages, which explains much of its growing adoption as supply has tightened.

Supply, policy, and shortages

Helium supply is concentrated in a few producing countries and a few large complexes. The United States has long been the largest producer, and the USGS's recent mineral summary estimates its output at 81 million cubic meters (2.9 billion cubic feet) valued at an estimated $970 million. Qatar is the other dominant source: according to the USGS, it produces about 30% of global helium supply. Known reserves outside the United States are led by Qatar, Algeria, and Russia, with Qatar at 10.1 billion cubic meters in the USGS's resource estimate. Concentration is more visible at the level of countries and individual sites, such as the Ras Laffan complex, than in plant counts. Because helium is a byproduct of natural gas production, when it's separated out by cryogenic distillation, output tracks gas production decisions and the health of the plants that process it.

The United States also operated a government stockpile, the Federal Helium Reserve, that dates to 1925, when Congress recognized the need to ensure that helium would be available for defense needs. The Helium Stewardship Act of 2013 then required the Bureau of Land Management to sell the system. Bidding took place in January 2024, and the BLM accepted two bids totaling $423,350,000 from Messer LLC. The sale closed in June 2024, and the BLM later transferred $460 million in proceeds from the sale to the U.S. Treasury. The change also moved data work: the BLM returned responsibility for collecting data and reporting helium production and consumption statistics to the USGS. Critics have argued about the sale's terms. Some say that the earlier practice of selling at below market rates discouraged private firms from expanding their own helium operations. A House committee also asked for information about the buyer's ties to a China-linked business, which is a matter the record does not settle.

The most acute disruption began in 2026. Iranian missiles struck Ras Laffan on March 18 and 19, damaging LNG trains and knocking out about 17% of Qatar's LNG export capacity. Because the gas was processed alongside helium, helium output stopped when the trains stopped. Exports face a second obstacle: the Strait of Hormuz is the only sea route for Qatari helium, and it has been effectively closed to commercial traffic. By August 2026, QatarEnergy had partially restarted its Helium2 plant at roughly 25% of normal capacity. Industry sources describe the shortage as the most severe on record, and one outlook puts full recovery estimates at three to five years. Russia's own export controls, effective 14 April 2026, removed another possible source of supply.

Market effects are reported with different magnitudes. One analysis says spot prices for helium have already doubled since the conflict began, while another reports that spot helium has cleared $1,000 per Mcf. A supply estimate from IndexBox puts the market's monthly gap at 5.2 million cubic metres, with spot prices rising 70–100 per cent. Analysts also expect that a prolonged disruption could push contract prices up 40–60%, which is slower than spot movements. The effect on large buyers is also disputed: Bank of America analysts argued that major industrial gas producers are relatively well insulated from direct supply disruption because of diversified sourcing and stockpiles.

The sources also differ on Qatar's share. Industry commentary gives it as about one-third of global supply, another says roughly 30% to 35%, and the USGS-based figure cited by AP is 30%. Recovery forecasts vary as well: one industry expert expects that when Qatari production returns to normal, helium supplies will return to the previous level. Checking such claims against official data is difficult because statistics lag events. The USGS's 2023 Minerals Yearbook chapter, for example, was released as an advance release in January 2026. For 2026 losses, readers should therefore compare industry estimates with the USGS Mineral Commodity Summaries as they are updated, and treat early market figures as provisional.

Applications

Helium's value in industry and research comes from a combination of properties: it is chemically inert, has the lowest boiling point of any substance, and is the second-lightest element. Its largest single use is as a refrigerant. Superconducting magnets in MRI scanners and in nuclear magnetic resonance spectrometers are wound from niobium-titanium wire that must be held near 4 K, and liquid helium, which boils at about 4.2 K at atmospheric pressure, is the standard coolant for keeping those magnets superconducting. Cryogenic engineers use the same principle in many other settings. Modern scanners increasingly use sealed magnets that recycle their helium with small cryocoolers, which reduces the volume of liquid needed, but the coolant remains essential to the design.

In semiconductor manufacturing, helium is used in several roles that depend on its inertness and thermal behavior. It is commonly introduced beneath silicon wafers during processing so that heat can be transferred evenly across the wafer surface, because helium conducts heat far better than most gases while leaving the wafer chemically unaffected. It is also used as a purge gas to flush chambers and transfer lines, and as a protective atmosphere that keeps reactive contaminants away from sensitive layers during fabrication of integrated circuits. These uses are less visible than MRI but consume a significant share of the gas in advanced fabrication plants.

Helium is also the standard tracer for leak detection. Because its atoms are very small and it is absent from most materials and from the air in meaningful amounts (roughly 5 parts per million by volume), a leak in a sealed system can be located by pressurizing the component with helium and sniffing the outside with a probe connected to a mass spectrometer tuned to helium. This method is used to test vacuum chambers, refrigeration circuits, aerospace hardware, fuel and gas lines, and sealed packaging, and it can detect leak rates far below what bubble tests or pressure-decay methods can reveal. Its use in this role is an example of the leak detection practice that has become standard in quality control.

Helium has several smaller but established uses. In welding, it serves as a shielding gas for arc processes such as gas tungsten arc welding, where it protects the molten metal from oxygen and nitrogen in the air. Because it conducts heat well, it produces a hotter arc than argon, which can be an advantage when welding thick aluminum or copper sections. In analytical laboratories, helium is widely used as the carrier gas in gas chromatography, moving sample molecules through the column without reacting with them and without interfering with detection. In the space and launch sector, helium pressurizes and purges the propellant tanks of rockets, including cryogenic tanks holding liquid hydrogen and liquid oxygen, because it remains a gas at very low temperatures and does not react with the propellants. Helium has also been used to fill airships, balloons, and other lighter-than-air craft; because it is non-flammable, it replaced hydrogen in most such applications after the early twentieth century, although its lifting power is lower.

Taken together, these applications explain why helium is treated as strategically important even though it is used in comparatively small volumes. Many of the uses above have no easily substituted alternative, especially cryogenic cooling for superconducting magnets, so demand is relatively insensitive to price changes. The same properties that make helium useful, its inertness and low boiling point, also make it difficult to capture, store, and recycle, which links the applications to the supply constraints discussed elsewhere in this entry.

Safety and health effects

Helium is chemically inert and non-toxic. It does not react with body tissue or interfere with metabolism, so its dangers are physical rather than poisonous. The most serious hazard is asphyxiation. Gas suppliers classify helium as a simple asphyxiant: while non-toxic, it can displace oxygen in confined spaces, creating asphyxiation risks. Industrial guidance usually treats 19.5% oxygen by volume as the lowest level at which people can work without breathing apparatus. Because helium is colourless, odourless and produces no irritation, a leak can build up unnoticed. Dizziness and impaired judgement come first, and when oxygen falls far enough, unconsciousness and death may occur in seconds and without warning. The usual precaution is therefore ventilation and oxygen monitoring, and rescuers entering a helium-filled space generally need self-contained breathing equipment.

Gas held in pressurised cylinders adds a mechanical hazard. Breathing directly from a high-pressure source can injure the lungs, and the gas can enter the bloodstream as bubbles, which may block vessels. The high pressure can cause gas embolism (bubbles in the bloodstream that can block blood vessels) or even rupture lung tissue. The risk is far greater from a tank than from a low-pressure party balloon. The familiar change in voice pitch after inhaling helium comes from the gas's low density and the high speed of sound within it, which alters the resonance of the vocal tract. In brief, incidental exposure this effect is harmless. Repeated or deliberate inhalation, however, carries the asphyxiation risk described above.

Helium's physical properties also matter in deep diving. Nitrogen dissolves readily in fatty tissue, and at depth it depresses the central nervous system, producing the state known as nitrogen narcosis. Helium is far less soluble and, in a mixture with oxygen, avoids this effect at the depths where it is normally used. Because of its reduced solubility, little helium is taken into cell membranes at high pressures, so helium does not have the narcotic effect that nitrogen does, and it also lowers the risk of bubble formation during decompression. Helium-oxygen mixtures, known as heliox, have therefore become standard for deep commercial and military dives. At greater depth the advantage carries a cost. Beyond roughly 150 metres of seawater, high-pressure nervous syndrome (HPNS) occurs during helium-oxygen diving at depths exceeding 150 msw and is characterized by CNS hyperexcitability, with manifestations such as tremor, myoclonus, and EEG changes. Its symptoms include nausea, dizziness and tremor. Slowing the compression rate and adding a small fraction of nitrogen to form trimix reduce these effects, a point noted in the diving literature.

Liquid helium, which boils at about 4 K (about −269 °C), is a separate hazard. Liquid helium causes injuries because of the rapid and profound cooling of the surrounding air, leading to the localized cold injury and cellular destruction. Contact with the liquid or with uninsulated pipes and vessels can produce freeze burns that resemble thermal burns, and the affected tissue may go numb because nerve function is disrupted. A reported case involved hand frostbite after a leak during a transfer from a storage dewar to a magnet system. Gloves give only limited protection, since liquid can seep through seams and cold surfaces can injure skin even when no liquid touches it. First aid for cold injuries generally involves gentle rewarming in water at about body temperature, with no rubbing and no dry heat. Liquid helium also expands enormously as it warms, roughly 750-fold in volume, so sealed containers need pressure relief valves and controlled venting to prevent rupture.

Research frontiers and open questions

Several open questions in helium research turn on helium-3, the rarer isotope that makes the coldest laboratory equipment work. Its scarcity now constrains both current experiments and proposed large-scale uses.

The most established use is in the dilution refrigerator, which relies on a mixture of helium-3 and helium-4. Below about 872 mK, a mixture that is roughly 67% helium-3 separates into a helium-3-rich phase and a helium-4-rich phase. Moving helium-3 from the concentrated phase into the dilute phase absorbs heat, much as evaporation does, and the device can cool continuously to about 2 mK with no moving parts in its cold section. Helium-3 is not burned in this process. It circulates in a sealed loop, so the main demand comes from filling each new machine and from losses during servicing. Dilution refrigerators are the most mature platform for quantum computers that operate near 10 mK, such as many designs based on superconducting qubits. Other architectures need far less cooling. Photonic systems, for example, can read out their states at 1–4 K, which requires only liquid helium-4.

Supply is the main constraint. Naturally occurring helium contains only about 2 ppm of helium-3, and it is not practical to extract it from natural gas in commercial quantities. Most of the supply comes from the decay of tritium, a radioactive hydrogen isotope that is produced in reactors and was stockpiled for nuclear weapons. Tritium decays into helium-3, and for decades the United States and the Soviet Union sold the helium-3 that accumulated in their reserves. After the Cold War, both countries reduced their tritium inventories, and the supply that remained became tied to government decisions and nuclear-security concerns. An ASCEND paper from NASA estimated that only about 100 kg of helium-3 was then readily available on Earth.

Prices have risen sharply, and sources disagree on the figures. A Science report described a fall from about $100 per liter to $3,000 during a single 2008 order and cited a current range of $1,000 to $20,000 per liter, depending on subsidies and discounts. A 2025 industry guide gave bulk prices of about $1,900 to $2,600 per liter and said that purified grades for dilution refrigerators can exceed $10,000. Differences in grade, volume, and whether a government sells at subsidized rates explain much of the variation. An earlier DOE study cited by Science projected demand of more than 65,000 liters a year against supply of 10,000 to 20,000 liters, but such forecasts are dated and depend on assumptions about future equipment. Researchers are therefore pursuing cooling alternatives. Adiabatic demagnetization refrigerators avoid helium-3 entirely, though the process is one-shot and can produce stray magnetic fields. Pulse-tube precooled "dry" dilution systems reduce the use of liquid helium, but they still depend on helium-3 for the cooling stage.

Proposals to mine the Moon for helium-3 are the most speculative part of this debate. The solar wind has implanted helium-3 into lunar regolith, and advocates argue that deuterium–helium-3 fusion would produce far fewer neutrons than deuterium–tritium fusion, reducing activation and radioactive waste. The resource estimates vary widely. One 2007 estimate placed total lunar reserves at about 6.5×10^8 kg, but the concentration in regolith is extremely low, so any recovery would require processing very large volumes of material. Critics point out that no fusion reactor has yet reached net energy gain, that deuterium–helium-3 reactions need higher temperatures and better plasma confinement than the deuterium–tritium route, and that transport costs and legal questions over lunar resources remain unresolved. Commercial timelines published by companies and promotional websites are therefore best treated as aspirations rather than established forecasts.

Work on the broader problem continues on several fronts. These include better recovery and recycling in laboratories, the development of helium-free or low-helium cryogenic systems, and more precise mapping of geological helium reserves. Each approach would reduce demand for helium-3 or improve the evidence needed to judge whether new supply sources are realistic.

References

1. Heliumbritannica.com
2. Helium - Chemistry Wikichemistry.miraheze.org
3. Heliumchemicool.com
4. Chemistry of Helium (Z=2) - Chemistry LibreTextschem.libretexts.org
5. Helium (He) - Discovery, Occurrence, Production, Properties and Applicationsazom.com
6. Liquid heliumen.wikipedia.org
7. WMI: Some Facts About Helium - Walther-Meißner-Institutwmi.badw.de
8. Heliumedu.rsc.org
9. Who Discovered Helium? - Universe Todayuniversetoday.com
10. This Day in History — Helium Is Discovered in the Suntheoffkeybard.com
11. Heliumen.wikipedia.org
12. The History of 'Helium': A Word Brought to You by a Solar Eclipsemerriam-webster.com
13. 150 years since the discovery of Helium - Science Museum Blogblog.sciencemuseum.org.uk
14. Up in the airshaastramag.iitm.ac.in
15. Today In Science History - August 18 - Discovery of Heliumsciencenotes.org
16. Pressure-dependent mechanical and thermodynamic properties of newly discovered cubic Na2Hearxiv.org
17. A stable compound of helium and sodium at high pressureqzhu2017.github.io
18. First astrophysical detection of the helium hydride ion (HeH$^+$)arxiv.org
19. Helium hydride ionen.wikipedia.org
20. Pressure-dependent mechanical and thermodynamic properties of newly discovered cubic Na2He - ScienceDirectsciencedirect.com
21. A stable compound of helium and sodium at high pressurenature.com
22. Helium forms stable molecules at high pressures - C&ENcen.acs.org
23. Synthesis of endohedral fullerenes by molecular surgerynature.com
24. X-ray observation of a helium atom and placing a nitrogen atom inside He@C60 and He@C70nature.com
25. Rational synthesis, enrichment, and (13)C NMR spectra of endohedral C(60) and C(70) encapsulating a helium atom - PubMedpubmed.ncbi.nlm.nih.gov
26. Synthesis of endohedral fullerenes by molecular surgery - PMCpmc.ncbi.nlm.nih.gov
27. Noble gas endohedral fullerenes - ScienceDirectsciencedirect.com
28. Activation energies and information entropies of helium penetration through fullerene walls. Insights into the formation of endofullerenes nX@C60/70 (n = 1 and 2) from the information entropy approach†pubs.rsc.org
29. The Dawn of Chemistryarxiv.org
30. Helium succumbs to pressurenature.com
31. 1 Heike Kamerlingh Onnes and the first liquefaction of heliumbibnum.education.fr
32. Liquid helium, superfluidityhyperphysics.phy-astr.gsu.edu
33. Superfluid Heliumlink.springer.com
34. January 1938: Discovery of Superfluidityaps.org
35. Heike Kamerlingh Onnes - New World Encyclopedianewworldencyclopedia.org
36. The discovery of superconductivity - Physics Todayphysicstoday.aip.org
37. Nobel Prize in Physics to Lee, Osheroff and Richardson for Discovery of Superfluidity in He 3 - Physics Todayphysicstoday.aip.org
38. The Nobel Prize in Physics 1996 - Advanced information - NobelPrize.orgnobelprize.org
39. Cornell physicists Robert Richardson and David Lee win 1996 Nobel Prize in Physicsnews.cornell.edu
40. Physics Nobel honors work on helium-3 superfluiditypubs.acs.org
41. Secrets of superfluid helium exploredas.cornell.edu
42. Big Bang nucleosynthesiscontent-calpoly-edu.s3.amazonaws.com
43. [1801.08023] Precision big bang nucleosynthesis with improved Helium-4 predictionsarxiv.org
44. Evidence for Enhanced Helium Enrichment from Asteroseismologyarxiv.org
45. A Bayesian direct method implementation to fit emission line spectra: Application to the primordial He abundance determinationarxiv.org
46. 1 24. Big Bang Nucleosynthesis 24. Big Bang Nucleosynthesispdg.lbl.gov
47. Solar eclipse of August 18, 1868en.wikipedia.org
48. Pierre Janssenen.wikipedia.org
49. Aug. 18, 1868: Helium is discoveredastronomy.com
50. Helium concentration in the earth's lower atmosphere - NASA Technical Reports Server (NTRS)ntrs.nasa.gov
51. The Helium Crisis: Real and Avoidable - Stanfordlarge.stanford.edu
52. Helium in Natural Gas - Occurrence and Productiongasliquids.com
53. Radiogenic helium concentration and isotope variations in crustal gas pools from Sichuan Basin, China - ScienceDirectsciencedirect.com
54. A huge helium shortage is looming — but ancient rocks in Earth's crust may be hiding massive reservoirslivescience.com
55. Where Does Helium Come From? Complete Guide to Sources 2025 - Business Performance and Innovation (BPI) Networkbpmforum.org
56. High helium reservoirs in the Four Corners area of the Colorado Plateau, USA - ScienceDirectsciencedirect.com
57. Helium dynamic accumulation process in the Hetianhe gas field, Tarim Basin, northwest China - ScienceDirectsciencedirect.com
58. Geological conditions, genetic mechanisms and accumulation patterns of helium resourcesped.cpedm.com
59. Why does helium released into the atmosphere ... - Vaiavaia.com
60. How Free Helium Forms, Migrates, and Gets Trapped - ScienceInsightsscienceinsights.org
61. Efficient Extraction of Helium from Natural Gas by Using ...aidic.it
62. Integrated process and apparatus for recovery of helium rich streamsimage-ppubs.uspto.gov
63. Process for recovering helium from a natural gas streamimage-ppubs.uspto.gov
64. Process for recovering helium from a gas streamimage-ppubs.uspto.gov
65. Helium extraction from natural gasimage-ppubs.uspto.gov
66. (PDF) Efficient Extraction of Helium from Natural Gas by Using Hydrogen Extraction Technologyresearchgate.net
67. Helium Recovery System - Bluefors.combluefors.com
68. Helium recovery and liquefactionheliumliquefier.com
69. Helium recovery systemmcgill.ca
70. HelioSmart Solutionsbruker.com
71. Mineral Commodity Summaries 2026 - Helium and Rare Gasespubs.usgs.gov
72. iran war helium shortage qatar chip supply chains ai boomdc.fortune.com
73. Prepared by Robert C. Goodin [(703) 648–7710, rgoodin@usgs.gov] HELIUMpubs.usgs.gov
74. BLM Helium System sale provides $460 million to U.S. Treasuryblm.gov
75. BLM accepts bids for the sale of Federal Helium Systemblm.gov
76. usgs seeks public comment helium supply riskusgs.gov
77. Impending sale of scientifically critical helium sparks worriesscience.org
78. Helium Shortage 2026: Supply Outlook, Pricing, and What Buyers Should Do Nowfusionww.com
79. Iran War Disrupts One-Third of Global Helium Supply - Exigerexiger.com
80. Qatari helium shortagesiumi.com
81. Iran war puts 'endangered' helium supplies at risk as Qatar halts exportsthenationalnews.com
82. The Iran war is threatening supply of a little-thought-of resource — helium. What it means for marketscnbc.com
83. myb1 2023 heliumpubs.usgs.gov
84. usgs estimates 306 billion cubic feet recoverable helium united statesusgs.gov
85. Oversight Committee Seeks Information After Biden Administration Sells U.S. Federal Helium System to CCP-Connected Business, Messer LLC - United States House Committee on Oversight and Government Reformoversight.house.gov
86. Helium - Crowcon Detection Instruments Limitedcrowcon.com
87. Gaseous heliumairproducts.com
88. Is Helium Toxic? - WestAirwestairgases.com
89. High-pressure neurologic syndromemedlink.com
90. Nitrogen Narcosis In Diving - StatPearls - NCBI Bookshelf - NIHncbi.nlm.nih.gov
91. Frostbite Injury of Hand Caused by Liquid Helium: A Case Report - PMCpmc.ncbi.nlm.nih.gov
92. Is Helium Dangerous? - WestAirwestairgases.com
93. HELIUM - HE MSDS EFFECTIVE DATE: FEBRUARY 7, 1997 PAGE 1 OF 7 MATERIAL SAFETYs3.us-east-1.wasabisys.com
94. High Pressure Diving Nervous Syndrome - MD Searchlightmdsearchlight.com
95. Gas Toxicity During Diving - Injuries and Poisoning - Merck Manual Consumer Versionmerckmanuals.com
96. Cryogenic Liquid Burns and Frostbite - Berkeley Lab EHSehs.lbl.gov
97. Cryogenic Liquid Safety - Office of Environmental Health and Safetyresearch.wayne.edu
98. Quantum Cryogenic Infrastructure and Helium-3 Guidepostquantum.com
99. Helium-3 in Quantum Computing: Hype vs. Realitypostquantum.com
100. Helium-3 Shortage Could Put Freeze On Low-Temperature Researchscience.org
101. As helium-3 runs scarce, researchers seek new ways to chill quantum computersscience.org
102. Cryogenic Systems for Quantum Photonic Technologies: A Practical Reviewarxiv.org
103. Dilution refrigeratoren.wikipedia.org
104. Helium phase separation refrigeratorimage-ppubs.uspto.gov
105. Systems and methods for electrostatic trapping of contaminants in cryogenic refrigeration systemsimage-ppubs.uspto.gov
106. 1 Lunar Helium-3: Mining Concepts, Extraction Research, and Potential ISRUntrs.nasa.gov
107. Lunar regolith processing system for mining and beneficiationimage-ppubs.uspto.gov
108. Prospecting for lunar Helium-3 with a radio-frequency atomic magnetometerarxiv.org
109. The Supply Chain Chokepoints in Quantumwarontherocks.com