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CHEMINFO Record Number: 147
CCOHS Chemical Name: Helium

Helium gas
Helium, compressed
Atomic helium
Helium, refrigerated liquid
Helium, refrigerated liquefied gas

Chemical Name French: Hélium
Chemical Name Spanish: Helio
CAS Registry Number: 7440-59-7
UN/NA Number(s): 1046 1963
RTECS Number(s): MH6520000
EU EINECS/ELINCS Number: 231-168-5
Chemical Family: Noble gas / inert gas
Molecular Formula: He
Structural Formula: He


Appearance and Odour:
Colourless, odourless gas or extremely cold liquid.(1,8)

Odour Threshold:
Not applicable. Odourless gas.

Warning Properties:
NONE - helium is odourless and non-irritating.

Helium is available commercially as a compressed gas or as a cryogenic liquid. Helium gas is available in grades with purity of 97.5 to 99.9999%.(9) Impurities may include small amounts of oxygen, nitrogen, argon, neon, hydrocarbon gases (e.g. methane), carbon dioxide and carbon monoxide.(9,10) Helium is transported by rail, road, water and air as a compressed gas at high pressures (at or above 16,550 kPa at 21 deg C) in cylinders, tank cars and tube trailers, and as a refrigerated liquefied gas in insulated cylinders, insulated portable and cargo tanks, and insulated intermodal containers.(9) Small amounts of refrigerated liquefied helium are shipped and stored in small portable, non-pressurized vacuum-jacketed vessels called Dewar flasks.(9) For shipping large quantities (greater than 5000 liters) of liquefied helium over great distances, non-vented pressurized containers are used.

Uses and Occurrences:
Helium is used as an inert shielding gas for arc welding. It is used to pressurize rocket fuels and force them into rocket engines, and to inert rocket motors; in large balloons for upper atmosphere and cosmic ray studies, in small balloons to carry meteorological instruments, and in airships; as a carrier gas in gas chromatography; in leak detection in refrigeration and other closed systems, and in plant construction and vacuum technology; as a heat transfer agent; as a diving gas; in laboratory and chemical research operations; to provide a protective atmosphere for growing germanium and silicon crystals for transistors, and in the production of reactive metals such as titanium and zirconium; as a coolant in high-temperature nuclear reactors; as a temperature standard; as a filler gas for neuron and gas thermometers, and cold-weather fluorescent lamps; in laser and fibre optic production; in counter tubes for the measurement of high-energy radiation; in medicine to improve the ease of breathing of asthmatics, and in gas mixtures used to investigate lung function. Helium is the major component of a gas mixture used in the carbon dioxide laser and is used in mixtures with neon and argon for electronic tubes and neon signs.(1,8,9,10)
Refrigerated liquefied helium is used in cryogenic technology as a refrigerant (e.g. for superconducting magnets); for magnetic resonance imaging tomography in medical diagnosis; low-temperature technology; in nuclear magnetic resonance (NMR) spectrometers; in particle accelerators; in magnetic separators, and for research in solid-state and high-energy physics. Other uses include cryopumps for ultrahigh vacuum, superconducting sensors (SQUID's), superconducting memories and circuit elements in computers, and low noise amplifiers.(8,9,10)
Helium is the second most abundant element in the universe after hydrogen and accounts for more than 25 mol % of the total cosmic material. On earth, the only practical sources of helium are the atmosphere and certain helium-bearing natural gases. Helium is also found in numerous minerals and rocks, particularly primitive rocks. It is produced in the decay of radioactive elements(8,10)


Colourless, odourless gas or extremely cold liquid. Will not burn. COMPRESSED GAS or REFRIGERATED, LIQUEFIED GAS. Cylinders or closed containers may rupture violently if heated. Air will condense on external surfaces, cooled by refrigerated liquefied helium, such as vessels or uninsulated pipes. The liquid air produced can result in oxygen-enrichment of the atmosphere, local to the equipment or in confined areas. Oxygen-enriched liquid air may cause a fire if it comes into contact with combustible surfaces or materials. Essentially non-toxic at normal temperature and pressure. Confined space hazard. Simple asphyxiant. High concentrations can displace oxygen in the air and cause suffocation. Compressed gas or refrigerated liquefied gas can cause cold burns or frostbite.


Effects of Short-Term (Acute) Exposure

Helium gas is not toxic at normal temperature and pressure. However, when helium is present in high concentrations in the air it acts as a simple asphyxiant. Simple asphyxiants displace oxygen in the air and can cause symptoms of oxygen deprivation (asphyxiation) when present in high enough concentrations to lower the oxygen concentration. The available oxygen should be a minimum of 18% or harmful effects will result.(2)
Helium gas can be liquefied under extreme pressures and very low temperatures. The gas can be released in very large quantities from pressurized tanks. If this happens in a confined space, or a space that is not well ventilated, the percentage of oxygen can very quickly drop to dangerous levels.
Effects of oxygen deficiency are: 12-16% - breathing and pulse rate are increased, with slight muscular incoordination; 10-14% - emotional upsets, abnormal fatigue from exertion, disturbed respiration; 6-10% - nausea and vomiting, inability to move freely, collapse, possible lack of consciousness; below 6% - convulsive movements, gasping, possible respiratory collapse and death. Since exercise increases the body's need for oxygen, symptoms will occur more quickly during exertion in an oxygen-deficient environment.(3,4) Survivors of oxygen deprivation may show damage to some or all organs including the central nervous system and the brain. These effects may or may not be reversible with time, depending on the degree and duration of the low oxygen and the amount of tissue injury.(4)

In occupational situations involving scuba diving, helium is often used in breathing gas mixtures. It does not cause a narcotic effect or narcosis, but can cause distortion of speech and increased conduction of body heat resulting in more rapid heat loss or in overheating at temperatures above 33-35 deg C.(5)

Skin Contact:
Helium gas is not irritating.
Direct contact with compressed helium gas or refrigerated liquefied helium may cause cold burns or frostbite (freezing of the tissue). Symptoms of mild frostbite include numbness, prickling and itching in the affected area. Symptoms of more severe frostbite include a burning sensation and stiffness of the affected area. The skin may become waxy white or yellow. Blistering, tissue death and gangrene may also develop in severe cases.
A case report describes quick freeze injury to both hands in a worker exposed to extremely cold liquefied helium and helium gas while he was refilling a machine with liquefied helium. At the time of exposure, he was protected with 2 mm thick leather gloves.(6) Another case report describes a worker who experienced severe freezing injury to his face, eyes, neck, chest, abdomen and arms from exposure to a large amount of extremely cold helium gas that leaked from a faulty cylinder valve and came into direct contact with his skin. He was not wearing any protective equipment.(7)

Eye Contact:
Helium gas is not irritating.
Direct contact with the compressed helium gas or refrigerated liquefied helium may cause freezing of the eye. Permanent eye damage or blindness could result.
In a case report, a worker experienced severe freezing injury to his upper body including his eyes from a large amount of super cold helium gas that leaked from a faulty cylinder valve. After 21-days, his eyesight had returned to normal.(7)

Ingestion exposure is not applicable to gases.

Effects of Long-Term (Chronic) Exposure

There is no human or animal information available. Helium is not expected to cause health effects following long-term exposure.


There is no human or animal information available. Helium is not expected to cause cancer.

The International Agency for Research on Cancer (IARC) has not evaluated the carcinogenicity of this chemical.

The American Conference of Governmental Industrial Hygienists (ACGIH) has not assigned a carcinogenicity designation to this chemical.

The US National Toxicology Program (NTP) has not listed this chemical in its report on carcinogens.

Teratogenicity and Embryotoxicity:
There is no human or animal information available. Helium is not expected to cause developmental effects.

Reproductive Toxicity:
There is no human or animal information available. Helium is not expected to cause reproductive effects.

There is no human or animal information available. Helium is not expected to be mutagenic.

Toxicologically Synergistic Materials:
There is no information available.

Potential for Accumulation:
Helium does not accumulate in the body.


In general, this gas has very low toxicity, but it can act as an asphyxiant at high concentrations. If the victim has been knocked down, wear appropriate protective equipment, and use the buddy system. Remove source of contamination or move victim to fresh air. If breathing is difficult, oxygen may be beneficial if administered by trained personnel, preferably on a doctor's advice. If breathing has stopped, trained personnel should begin artificial respiration (AR) or, if the heart has stopped, cardiopulmonary resuscitation (CPR) immediately. Quickly transport victim to an emergency care facility.

Skin Contact:
COMPRESSED GAS OR REFRIGERATED LIQUEFIED GAS: Quickly remove victim from source of contamination and briefly flush with lukewarm, gently flowing water until the chemical is removed. DO NOT attempt to rewarm the affected area on site. DO NOT rub area or apply dry heat. Gently remove clothing or jewelry that may restrict circulation. Carefully cut around clothing that sticks to the skin and remove the rest of the garment. Loosely cover the affected area with a sterile dressing. DO NOT allow the victim to drink alcohol or smoke. Immediately obtain medical attention. GAS: Not applicable. No effects expected.

Eye Contact:
COMPRESSED GAS OR REFRIGERATED LIQUEFIED GAS: Quickly remove victim from source of contamination. Immediately and briefly flush with lukewarm, gently flowing water until the chemical is removed. DO NOT attempt to rewarm. Cover both eyes with a sterile dressing. DO NOT allow victim to drink alcohol or smoke. Immediately obtain medical attention. GAS: Not applicable. No effects expected.

Ingestion is not an applicable route of exposure for gases.

First Aid Comments:
Ingestion is not an applicable route of exposure for gases.

Note to Physicians:
Provide general supportive measures (comfort, warmth, rest). Consult a doctor and/or the nearest Poison Control Centre for all exposures except minor instances of inhalation. Some recommendations in the above sections may be considered medical acts in some jurisdictions. These recommendations should be reviewed with a doctor and appropriate delegation obtained, as required. All first aid procedures should be periodically reviewed by a doctor familiar with the material and its condition of use in the workplace.


Flash Point:
Non-flammable gas.

Lower Flammable (Explosive) Limit (LFL/LEL):
Not applicable

Upper Flammable (Explosive) Limit (UFL/UEL):
Not applicable

Autoignition (Ignition) Temperature:
Not applicable

Sensitivity to Mechanical Impact:
Not sensitive. Stable gas or refrigerated liquid.

Sensitivity to Static Charge:
Specific information is not available. Refrigerated liquefied helium will not accumulate static charge, since it is a superconducting liquid. Since it is non-flammable, helium will not be ignited by a static charge.

Electrical Conductivity:
Not available

Minimum Ignition Energy:
Not applicable

Combustion and Thermal Decomposition Products:
None known

Fire Hazard Summary:
Helium does not burn. Compressed gas. If involved in a fire, heat can cause a rapid build-up of pressure inside cylinders, which may cause explosive rupture and a sudden release of large amounts of helium gas or may cause cylinder to rocket. High concentrations of helium can displace oxygen in the air, causing suffocation (simple asphyxiant). Refrigerated liquefied gas. The volume of a given quantity of refrigerated liquefied helium at 101.33 kPa and -268 deg C increases 745 times when warmed to room temperature.(11) This rapid expansion in sealed non-vented containers (e.g. cold traps) can cause the vessel to burst. Refrigerated liquefied helium can be particularly dangerous during fires because of its potential to rapidly freeze water, possibly blocking pressure relief valves. If large concentrations of cold helium gas are present, water vapour in the surrounding air will condense, creating a dense fog that may make it difficult to find fire exits or equipment. Because of the extremely cold temperature of refrigerated liquefied helium, there is a danger of air liquefaction and oxygen-enrichment . Air will condense on external helium-cooled surfaces, such as vessels, or exposed or uninsulated or poorly insulated pipes. Oxygen-enrichment of the atmosphere may occur locally to the equipment or in confined areas. Oxygen-enriched liquid air may cause a fire if it comes into contact with combustible surfaces or materials.(9,12)

Extinguishing Media:
Use extinguishing media suitable for the surrounding fire.

Fire Fighting Instructions:
Evacuate area and fight fire from a safe distance or a protected location.
If a fire occurs in an area where helium cylinders, containers and/or tanks are used or stored, move cylinder or other containers from the fire area only if it can be done without risk. Use extreme caution since heat may rupture cylinders, which may rocket. Otherwise, carefully use water in large quantities, preferably in spray form, to cool fire-exposed cylinders, containers or tanks and equipment and this should begin as soon as possible (within the first several minutes) and should concentrate on any unwetted portions of the container. No part of a cylinder should be subjected to a temperature higher than 52 deg C (approximately 125 deg F). Take care not to block pressure relief valves. Most cylinders and other containers are provided with a pressure relief valve designed to vent contents when they are exposed to elevated temperatures. Stay away from ends of tanks, but be aware that flying material from ruptured tanks may travel in any direction. Withdraw immediately in case of rising sounds from venting safety device or any discolouration of tanks due to fire.
Refrigerated liquefied helium gas can be particularly dangerous during fires because of its potential to liquify air with oxygen enrichment. Do not enter areas if oxygen enrichment is possible, since a serious fire and explosion risk exists. Withdraw immediately and fight fire from a protected location.
Contact with refrigerated liquified helium gas can also rapidly freeze water. If possible, avoid spraying cold areas of equipment to avoid rapid freezing of water, which can result in heavy icing and possible blockage of pressure release valves. If it is desirable to evaporate a liquefied helium spill quickly, water spray may be used to increase the rate of evaporation if the increased vapour evolution can be controlled. DO NOT discharge a solid stream of water into liquefied helium. If liquefied helium is discharging into the air, judgment should be used in deciding whether to allow the gas to escape, with the possible risk of asphyxiation, or to attempt to cut off the gas flow, depending on which is safer. Where asphyxiation is not a factor, it is preferable to let the gas escape.

Protection of Fire Fighters:
Helium gas is an asphyxiant. The refrigerated liquid is a cryogenic. Firefighters may enter the area if positive pressure self-contained breathing apparatus (NIOSH approved or equivalent) and full Bunker Gear is worn. Protect against any skin contact with the refrigerated liquid.


NFPA - Comments:
NFPA has no listing for this chemical in Codes 49 or 325.


Molecular Weight: 4.003

Conversion Factor:
1 ppm = 0.16 mg/m3; 1 mg/m3 = 6.12 ppm at 25 deg C (calculated)

Physical State: Gas
Melting Point: Not applicable.
Boiling Point: -268.94 deg C (-452.1 deg F) (9)
Relative Density (Specific Gravity): Not applicable (gas)
Solubility in Water: Very slightly soluble (0.94 mL/100 mL at 0 deg (9); 0.17 mg/100 g at 0 deg C (13); 0.16 mg/100 g at 20 deg C (13))
Solubility in Other Liquids: Very slightly soluble in ethanol, methanol, acetone, benzene and aliphatic hydrocarbons, e.g. pentane, hexane and heptane. The solubility in aliphatic hydrocarbons is usually higher than in oxygen-containing solvents.(13)
Coefficient of Oil/Water Distribution (Partition Coefficient): Log P(oct) = 0.28 (experimental) (15)
pH Value: Not applicable
Viscosity-Dynamic: Not applicable
Surface Tension: Not applicable for gas. Liquid: 0.34 mN/m (0.34 dynes/cm) at -271 deg C.(1)
Vapour Density: 0.138 at 21 deg C and 101.3 kPa (air = 1) (1)
Vapour Pressure: Not applicable (entirely gaseous above -268 deg C).
Vapour Pressure at 50 deg C: Greater than 7000 kPa (69 atm) (estimated from graph) (1)
Saturation Vapour Concentration: Not applicable
Evaporation Rate: Not applicable (gas). Refrigerated liquefied gas will rapidly return to the gas phase.
Critical Temperature: -267.9 deg C (-450.3 deg F) (1,9)
Critical Pressure: 227.9 kPa (2.25 atm) (1)

Other Physical Properties:
The temperature of refrigerated liquefied helium is cold enough to condense and freeze all other gases. Therefore, there is a danger that the solidified gases can plug pipes, vents, valves or small openings and cause equipment failure.(9,12)


Stable gas or refrigerated liquefied gas.

Hazardous Polymerization:
Does not occur.

Incompatibility - Materials to Avoid:

NOTE: Chemical reactions that could result in a hazardous situation (e.g. generation of flammable or toxic chemicals, fire or detonation) are listed here. Many of these reactions can be done safely if specific control measures (e.g. cooling of the reaction) are in place. Although not intended to be complete, an overview of important reactions involving common chemicals is provided to assist in the development of safe work practices.

Helium is a noble or rare gas and does not react with other elements or chemical compounds under ordinary conditions.(1,9)

Hazardous Decomposition Products:

Conditions to Avoid:
Liquid helium must not be allowed to come unto contact with air.(9)

Corrosivity to Metals:
Helium gas is not corrosive to the common metals, including stainless steel (e.g. types 18-8, 301, 304, 316 and 430), aluminum (types 3003, 5052 and 6061-T6), carbon steel (types 1010 and 1020), nickel-base alloys, like Hastelloy, brass, bronze and tantalum.(16) At the extremely low temperature of liquid helium, ordinary carbon steels and most alloys steels become brittle and are likely to break without warning. Satisfactory metals for use with liquid helium include high-alloy stainless steels, like type 18-8 stainless steel and other austenitic nickel-chromium alloys, copper, nickel-base alloy, Monel, brass and aluminum).(9)

Corrosivity to Non-Metals:
Helium gas does not attack plastics, like Teflon and other fluorocarbons, chlorinated polyvinyl chloride (CPVC), polyvinyl chloride (PVC), polypropylene, nylon, polyurethane, high density polyethylene and polystyrene (17); and elastomers, like ethylene propylene, butyl rubber, Viton and other fluorocarbons, like Chemraz and Kalrez, nitrile Buna-N, chloroprene, styrene butadiene (SBR), polyurethane, isoprene, natural rubber and low density polyethylene.(14)


Helium gas is essentially non-toxic at normal temperature and pressure. Therefore, very little information from animal toxicity testing is available.
A few studies designed to evaluate the effects of pressure using helium-oxygen as the breathing gas mixture were located. These studies are not relevant to the toxicity of helium except possibly for occupational situations involving scuba diving.


Selected Bibliography:
(1) Yaws, C.L. Helium. In: Matheson gas data book. 7th ed. McGraw Hill, 2001. p. 401-406
(2) American Conference of Governmental Industrial Hygienists (ACGIH). Helium gas. Documentation of the Threshold Limit Values for Chemical Substances. 7th ed. American Conference of Governmental Industrial Hygienists, 2001
(3) Leikauf, G.D., et al. Inorganic compounds of carbon, nitrogen and oxygen. In: Patty's Industrial Hygiene and Toxicology. 5th ed. Vol. 3. Edited by E. Bingham, et al. John Wiley & Sons, 2001
(4) Wilkenfeld, M. Simple asphyxiants. In: Environmental and Occupational Medicine. 3rd ed. Edited by W.N. Rom. Lippincott-Raven Publishers, 1998. p. 651-655
(5) The physician's guide to diving medicine. Edited by C.W. Shilling, et al. Plenum Press, 1984. p. 128-135, 223-272, 283-331
(6) Kumar, P., et al. Helium vapour injury: a case report. Burns. Vol. 25, no. 3 (May 1999). p. 265-268
(7) Kuyven, C.R., et al. Major burn injury caused by helium vapour. Burns. Vol. 29, no. 2 (Mar. 2003). p. 179-181
(8) Häussinger, P., et al. Noble gases. In: Ullmann's encyclopedia of industrial chemistry. 7th ed. John Wiley and Sons, 2002. Also available at: <> (Subscription required)
(9) Compressed Gas Association. Helium. In: Handbook of compressed gases. 4th ed. Kluwer Academic Publishers, 1999. p. 408-414
(10) Hwang, S-C., et al. Helium group gases. In: Kirk-Othmer encyclopedia of chemical technology. John Wiley and Sons, 1995. Available at: <> (Subscription required)
(11) Compressed Gas Association. Safety considerations for compressed gases and cryogenic liquids. In: Handbook of compressed gases. 4th ed. Kluwer Academic Publishers, 1999. p. 16-39
(12) British Cryogenics Council. Cryogenics safety manual: a guide to good practice. 3rd ed. Butterworth Heinemann, 1991. p. 1-26, 94-100
(13) Clever, H.L., ed. International Union of Pure and Applied Chemistry (IUPAC) Solubility data series. Vol. 1. Helium and neon: gas solubilities. Pergamon Press, 1979
(14) Pruett, K.M. Chemical resistance guide for elastomers II: a guide to chemical resistance of rubber and elastomeric compounds. Compass Publications, 1994. p. C-176 to C-181
(15) Syracuse Research Corporation. Interactive LogKow (KowWin) Database Demo. Date unknown. Available at: <>
(16) Pruett, K.M. Chemical resistance guide to metals and alloys: a guide to chemical resistance of metals and alloys. Compass Publications, 1995. p. 158-169
(17) Pruett, K.M. Chemical resistance guide for plastics: a guide to chemical resistance of engineering thermoplastics, fluoroplastics, fibers and thermoset resins. Compass Publications, 2000. p. 230-241

Information on chemicals reviewed in the CHEMINFO database is drawn from a number of publicly available sources. A list of general references used to compile CHEMINFO records is available in the database Help.

Review/Preparation Date: 2005-03-25

Revision Indicators:
Vapour pressure at 50 deg C 2006-01-17
Relative density 2006-09-28

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