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CHEMINFO Record Number: 75
CCOHS Chemical Name: Methane

Methane, compressed gas
Methyl hydride
Marsh gas
Fire damp
Methane, refrigerated liquid

Chemical Name French: Méthane
Chemical Name Spanish: Metano
CAS Registry Number: 74-82-8
UN/NA Number(s): 1971
RTECS Number(s): PA1490000
EU EINECS/ELINCS Number: 200-812-7
Chemical Family: Saturated aliphatic hydrocarbon / n-alkane / paraffin / methane
Molecular Formula: C-H4
Structural Formula: CH4


Appearance and Odour:
Colourless, odourless gas.(5,17) Commercial methane may have an added odourant (consult supplier MSDS).

Odour Threshold:
Odourless (5,17); odorant may be added by supplier.

Warning Properties:
POOR - odourless; odorant may be added by supplier.

Technical and higher grades of methane are at least 98% pure and are not odourized. These grades contain trace impurities such as nitrogen, hydrogen, oxygen, water, carbon monoxide, carbon dioxide, ethane, propane and propylene.(5,21)

Uses and Occurrences:
Methane is the major constituent of natural gas, which is a heating fuel widely used by residential and commercial markets. It is also used to make synthesis gas, which is a mixture of hydrogen and carbon monoxide gases. The synthesis gas is then used in the production of methanol, acetic acid and acetic anhydride, ammonia, halogenated methanes, and for chemical vapour deposition of carbide and diamond films. The main source of methane is natural gas, which is essentially of biological origin and is found in geological gas reservoirs, crude oil wells, coal mines, marshland, agricultural sites, sewage sludge, and landfills.(21,23)


Pure methane is a colourless and odourless gas (odorant may be added by supplier). EXTREMELY FLAMMABLE GAS. COMPRESSED GAS or REFRIGERATED LIQUEFIED GAS. May cause a flash fire. Essentially non-toxic at low concentrations. Asphyxiant. At high concentrations, methane can reduce oxygen available for breathing. Confined space hazard. Can accumulate in confined spaces, producing a fire and asphyxiation hazard. Direct contact with refrigerated liquefied gas or compressed gas escaping from its cylinder can cause cold burns or frostbite.


Effects of Short-Term (Acute) Exposure

Methane is not toxic below the lower explosive limit of 5% (50000 ppm). However, when methane is present at high concentrations, it acts as an asphyxiant. Asphyxiants displace oxygen in the air and can cause symptoms of oxygen deprivation (asphyxiation). The available oxygen should be a minimum of 18% or harmful effects will result.(3,11) Methane displaces oxygen to 18% in air when present at 14% (140000 ppm). It is not expected to cause unconsciousness (narcosis) due to central nervous system depression until it reaches much higher concentrations (30% or 300000 ppm) - well above the lower explosive limit and asphyxiating concentrations.(13)
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.(3,11) 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.(3)
Some closely related aliphatic hydrocarbons (propane, butane and isobutane) may be weak cardiac sensitizers in humans following inhalation exposures to high concentrations (greater than 5% for isobutane and greater than 10% for propane). Cardiac sensitizers may cause the sudden onset of an irregular heartbeat (arrhythmia) and, in some cases, sudden death. Sudden deaths have been reported in cases of substance abuse involving butane and propane. Under stressful conditions and with exposure to high concentrations, the effects of cardiac sensitization may be important for some hydrocarbon gases. The asphyxiant effects of methane may enhance cardiac sensitization.(12)

Skin Contact:
Methane gas is not a skin irritant.
Contact with the refrigerated liquefied gas or compressed gas escaping from its cylinder may cause cold burns or frostbite. 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.

Eye Contact:
Methane gas does not irritate the eyes.
Contact with the refrigerated liquefied gas or compressed gas escaping from its cylinder may cause cold burns or freezing of the eye. Permanent eye damage or blindness could result.

Not applicable to gases.

Effects of Long-Term (Chronic) Exposure

No human or animal information was located. Harmful effects are not expected following long-term exposure.


No human or animal information was located. Methane 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:
No human information was located. No conclusions can be drawn based on the one limited animal study located.

Reproductive Toxicity:
No human or animal information was located. Methane is not expected to cause reproductive toxicity.

No information was located.

Toxicologically Synergistic Materials:
No information was located.

Potential for Accumulation:
Does not accumulate


This is chemical is extremely flammable. Take proper precautions (e.g. remove any sources of ignition). 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, trained personnel should administer emergency oxygen. If breathing has stopped, trained personnel should begin artificial respiration (AR) or, if the heart has stopped, cardiopulmonary resuscitation (CPR) or automated external defibrillation (AED) immediately. Quickly transport victim to an emergency care facility.

Skin Contact:
REFRIGERATED LIQUEFIED GAS / COMPRESSED GAS: Quickly remove victim from source of contamination and briefly flush with lukewarm, gently flowing water. 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. Obtain medical attention immediately. GAS: Not applicable. No effects expected.

Eye Contact:
REFRIGERATED LIQUEFIED GAS / COMPRESSED GAS: Quickly remove victim from source of contamination. Immediately and briefly flush with lukewarm, gently flowing water. 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:
Provide general supportive measures (comfort, warmth, rest).
Consult a doctor and/or the nearest Poison Control Centre for all serious exposures.
Some first aid procedures recommended above require advanced first aid training. Protocols for undertaking advanced procedures must be developed in consultation with a doctor and routinely reviewed.
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:
Flammable gas

Lower Flammable (Explosive) Limit (LFL/LEL):
5.0% (1,6)

Upper Flammable (Explosive) Limit (UFL/UEL):
15.4% (1,6)

Autoignition (Ignition) Temperature:
537 deg C (999 deg F) (1,6)

Sensitivity to Mechanical Impact:
Not sensitive.

Sensitivity to Static Charge:
Liquefied methane can accumulate electrostatic charge by flow, friction in pipes, splashing or agitation. Methane gas in the flammable range can be easily ignited by an electrostatic discharge of sufficient energy (e.g. brush discharge).

Electrical Conductivity:
Not applicable for gas. Not available for liquefied gas. The electric conductivity for liquefied methane is expected to be less then 50 pS/m, based on methane's chemical properties and dielectric constant.

Minimum Ignition Energy:
0.21 mJ for 8.5% by volume (6)

Combustion and Thermal Decomposition Products:
Carbon monoxide, carbon dioxide, and water.

Fire Hazard Summary:
EXTREMELY FLAMMABLE GAS. It can also be a COMPRESSED GAS OR REFRIGERATED LIQUEFIED GAS. Can readily form explosive mixtures with air, which are easily ignited by a static charge. Liquefied methane accumulates static charge. Liquefied methane gas vapourizes under normal conditions and produces 600 volumes vapour for every one volume of liquid. A major release of liquefied methane will produce a large vapour cloud due to condensation of moisture. Small spills of liquefied methane tend to rise and diffuse rapidly above the leak. Large spills of liquefied methane behave like dense flammable vapours and travel over long distances creating a flash back hazard. Direct addition of water (or any other room temperature liquid) to the liquefied gas will cause flash vapourization resulting in an explosion (either immediately or delayed) known as a "boiling liquid, expanding vapour explosion (BLEVE)".(27,28) The gas can accumulate in confined spaces, resulting in an explosion or asphyxiation hazard. During a fire, toxic gases may be generated. Heat from a fire can cause a rapid build-up of pressure inside cylinders or tanks, which may cause explosive rupture and a sudden release of large amounts of extremely flammable gas.

Extinguishing Media:
Dry chemical powder and high-expansion foam. Foam manufacturers should be consulted for recommendations regarding types of foams and application rates.(27,28)

Extinguishing Media to be Avoided:
Carbon dioxide, low expansion foams, and direct application of water on liquefied methane gas. Under certain conditions, discharge of carbon dioxide produces electrostatic charges that could create a spark and ignite methane.(27,30)

Fire Fighting Instructions:
Evacuate area. Fight fire from a protected location or maximum distance possible. Approach fire from upwind to avoid toxic decomposition products.
For fires involving flammable gases, the best procedure is to stop the flow of gas before attempting to extinguish the fire. It is extremely dangerous to extinguish the fire, while allowing continued flow of the gas. The gas could form an explosive mixture with air and re-ignite resulting in a sudden violent flash fire, which may cause far more damage than if the original fire had been allowed to burn. In some cases, extinguishing the fire with dry chemical powder may be necessary to permit immediate access to valves to shut off the flow of gas. However, this must be done carefully. If it is not possible to stop the flow of gas and if there is no risk to the surrounding area, allow the fire to continue burning while protecting exposed materials with water spray, to prevent ignition of other combustible materials.
DO NOT direct water spray into liquefied gas. Liquefied methane gas spills clouds may be controlled with high-expansion foam blankets. The resulting foam solutions may be flammable. Dike for appropriate disposal. Cryogenic liquids can be particularly dangerous during fires because of their potential to rapidly freeze water. Avoid spraying cold areas of containers or equipment to avoid rapid freezing of water, which can result in heavy icing and possible blockage of pressure release valves.
Heat from a fire can cause a rapid build-up of pressure inside cylinders or tanks, which may cause explosive rupture. Withdraw immediately in case of rising sound from venting safety device or any discolouration of tank due to fire.
Cool fire-exposed cylinders, tanks, equipment or pipelines by applying hose streams, to minimize the risk of rupture. Cooling should begin as soon as possible (within several minutes) and should concentrate on any unwetted portions of the container. Apply water from the side and a safe distance. DO NOT direct water at open or leaking cylinders and take precautions not to get water inside a container or cylinder. Reverse flow into cylinder may cause rupture. No part of a cylinder should be subjected to a temperature higher than 52 deg C (approximately 125 deg F). Cooling should continue until well after the fire is out.
Isolate cylinders and other containers exposed to heat but not yet directly involved in the fire and protect personnel. Move cylinders from fire area only if this can be done without risk. Stay away from ends of tanks, but be aware that flying material (shrapnel) from ruptured tanks or cylinders may travel in any direction.
For an advanced or a massive fire in a large area, use unmanned hose holder or monitor nozzles; if this is not possible withdraw from fire area and allow fire to burn.
After the fire has been extinguished, the resulting foam solutions of methane are flammable. Explosive atmospheres may be present. Before entering such an area, especially confined areas, check the atmosphere with an appropriate monitoring device. Cylinders or tanks that have been involved in a fire should not be approached until they have been completely cooled down.

Protection of Fire Fighters:
Methane is only slightly hazardous to health. However, it can displace oxygen, reducing the amount available for breathing. Firefighters may enter the area if positive pressure self-contained breathing apparatus (NIOSH approved or equivalent) and full Bunker Gear is worn.


NFPA - Health: 2 - Intense or continued (but not chronic) exposure could cause temporary incapacitation or possible residual injury.
NFPA - Flammability: 4 - Will rapidly or completely vaporize at atmospheric pressure and normal ambient temperature, or readily disperse in air and burn readily.
NFPA - Instability: 0 - Normally stable, even under fire conditions, and not reactive with water.


Molecular Weight: 16.04

Conversion Factor:
1 ppm = 0.655 mg/m3; 1 mg/m3 = 1.53 ppm at 25 deg C (calculated)

Physical State: Gas
Melting Point: -182 deg C (-296 deg F) (29)
Boiling Point: -162 deg C (-259 deg F) (29)
Relative Density (Specific Gravity): Not applicable (gas)
Solubility in Water: Practically insoluble (22 mg/L) at 25 deg C (29)
Solubility in Other Liquids: Soluble in ethanol; slightly soluble in ether and chloroform.(26)
Coefficient of Oil/Water Distribution (Partition Coefficient): Log P(oct) = 1.09 (29)
pH Value: Not applicable
Vapour Density: 0.555 (air = 1) (1)
Vapour Pressure: Not applicable
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
Henry's Law Constant: 0.67 X 10(5) Pa.m3/mol (cited as 0.658 atm.m3/mol) at 25 deg C (29); log H = 1.43 (dimensionless constant; calculated)
Critical Temperature: -82 deg C (-116 deg F) (1,5)
Critical Pressure: 4,640 kPa (45.9 atm) (1,5)

Other Physical Properties:
DIELECTRIC CONSTANT: 1 at 27 deg C (calculated) (25)



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.

The risk of a hazardous incident occurring due to accidental mixing of methane with other substances is low because methane only reacts with a very small number of chemical classes that are commonly used in the workplace. If an accidental mixing does occur, these few reactions may be severe.

STRONG OXIDIZING AGENTS (e.g. peroxides, perchlorates) - Increases the risk of fire and explosion. Reaction may be delayed.(22,23)
HALOGEN COMPOUNDS (e.g. chlorine, and bromine) - Risk of fire and explosion. Fluorine gas reacts explosively.(20) Mixtures with 20% or more of chlorine are explosive. However, if any mixture of methane and chlorine gas is exposed to direct sunlight there is almost always an explosion.(15) The presence of some metallic salts or oxides (e.g. ferric chloride, copper oxide) or metals (e.g. mercury, zinc) increases the reactivity with the halogen compounds.(15,19) Reaction with iodine is not vigorous.(24)

Hazardous Decomposition Products:

Conditions to Avoid:
Static discharge, sparks, open flames and other ignition sources

Corrosivity to Metals:
Pure methane gas is not corrosive to aluminum or carbon steel.(18)

Corrosivity to Non-Metals:
Pure methane gas is corrosive to acrylonitrile butadiene styrene(ABS), high-density and ultra high molecular weight polyethylene (HDPE) and is slightly corrosive to polypropylene. Methane gas is not corrosive to fluorinated plastics, polyamides, polyvinyl chloride(PVC) and polyacetals.(14)


No standard animal toxicity values are available.

Effects of Short-Term (Acute) Exposure:

It has been reported that 87% (870000 ppm) caused anesthesia (unconsciousness) in mice, while 90% (900000 ppm) caused irregularities of respiration and respiratory arrest. Rabbits inhaled a mixture of 80% (800000 ppm) methane and 20% oxygen (cited as 4 volumes methane and 1 volume oxygen) without showing any ill effects.(2, unconfirmed) These observations are based on historical reports and there are insufficient details available for evaluation.

Teratogenicity, Embryotoxicity and/or Fetotoxicity:
No conclusions can be drawn based on the only study located.
Mice (30/group) were exposed to 0, 5, 7.5 or 8% fuel-gas (composition not defined, but expected to contain 85% methane) on days 8-13 of pregnancy. Oxygen concentrations were not maintained. At 8%, 11 mothers died. A number of effects in the offspring were described, but the data was not statistically analyzed.(10)


Selected Bibliography:
(1) Yaws, C.L. Matheson gas data book. 7th ed. McGraw-Hill, 2001. p. 516-521, 879 (Appendix 5)
(2) Von Oettingen, W.F. Toxicity and potential dangers of aliphatic and aromatic hydrocarbons : a critical review of the literature. Public Health Bulletin. No. 255 (1940)
(3) Wilkenfeld, M. Simple asphyxiants. In: Environmental and Occupational Medicine. 3rd ed. Edited by W.N. Rom. Lippincott-Raven Publishers, 1998. p. 651-655
(4) Ethel Browning's toxicity and metabolism of industrial solvents. 2nd ed. Vol. I : hydrocarbons. Elsevier, 1987. p. 255-257
(5) Compressed Gas Association. Handbook of compressed gases. 4th ed. Kluwer Academic Publishers, 1999. p. 488-495
(6) Fire protection guide to hazardous materials. 13th ed. Edited by A.B. Spencer, et al. National Fire Protection Association, 2002. NFPA 77, NFPA 325, NFPA 497
(7) Forsberg, K., et al. Quick selection guide to chemical protective clothing. 4th ed. Van Nostrand Reinhold, 2002
(8) European Economic Community. Commission Directive 93/72/EEC. Sept. 1, 1993
(9) NIOSH pocket guide to chemical hazards. NIOSH, June 1994. p. 262-263
(10) Kato, T. Embryonic abnormalities of the central nervous system caused by the fuel-gas inhalation of the mother animal. Folia Psychiatrica et Neurologica. Japonica. Vol. 11, no. 4 (1958). p. 301-324
(11) Leikauf, G.D., et al. Inorganic compounds of carbon, nitrogen and oxygen. In: Patty's Toxicology. Edited by G.D. Clayton, et al. 5th ed. John Wiley & Sons, 2001
(12) Aliphatic hydrocarbon gases: alkanes (C1-C4). In: Documentation of threshold limit values and biological exposure indices. 7th ed. (Suppl.). American Conference of Governmental Industrial Hygienists, 2004
(13) Drummond, I. Light hydrocarbon gases: a narcotic, asphyxiant, or flammable hazard? Applied Occupational and Environmental Hygiene. Vol. 8 (1993). p. 120-125
(14) Pruett, K.M. Chemical resistance guide for plastics: a guide to chemical resistance of engineering thermoplastics, fluoroplastics, fibers and thermoset resins. Compass Publications, 2000
(15) Egloff, G. The halogenation of the paraffin hydrocarbons. Chemical Reviews. Vol. VIII, no. 1 (1930). p. 1-80
(16) Steacie, E.W.R. The kinetics of elementary reactions of the simple hydrocarbons. Chemical Reviews. Vol. 22, no. 2. (1938). p. 311-402
(17) Klopping, H.L. Olfactory theories and the odors of small molecules. Journal of Agricultural Food Chemistry. Vol. 19, no. 5 (1971). p. 999-1004
(18) Pruett, K.M. Chemical resistance guide to metals and alloys: a guide to chemical resistance of metals and alloys. Compass Publications, 1995. p. 206-217
(19) Thomas, C.L. et al. Reactions of hydrocarbons in electrical discharges. Chemical Reviews. Vol. 28, no. 1 (1941). p. 1-70
(20) Hauge, R.H. et al. Studies of the reaction of molecular fluorine with methane, acetylene, ethylene, allene, and other small hydrocarbons in matrices at low temperatures. Journal of the American Chemical Society. Vol. 101, no. 23 (1979). p. 6950
(21) Nyns, E.J. Methane. In: Ullmann's encyclopedia of industrial chemistry. Available at: <> {Subscription required}
(22) Griesbaum, K. Saturated hydrocarbons. In: Ullmann's encyclopedia of industrial chemistry. Available at: <> {Subscription required}
(23) Mears, D.E. et al., Hydrocarbons. In: Kirk-Othmer encyclopedia of chemical technology. Available at: <> {Subscription required}
(24) Crabtree, R.H. Aspects of methane chemistry. Chemical Reviews. Vol. 95 (1995). p. 987-1007
(25) Youngglove, B.A. et al. Thermophysical properties of fluids. Methane. Journal of Physical Chemistry Reference Data. Vol. 16. no. 4 (1987). p. 582-589
(26) Lide, D.R., ed. Handbook of chemistry and physics. 82nd ed. CRC Press, 2001. p. 3-205
(27) Recommended practice for responding to hazardous materials incidents. National Fire Protection Association, 2002. NFPA 471
(28) A guide to the safe handling of hazardous materials accidents. 2nd ed. Manual 10. American Society for Testing and Materials (ASTM), 1990
(29) Syracuse Research Corporation. The Physical Properties Database (PHYSPROP). Interactive PhysProp Database Demo. Date unknown. Available at: <>
(30) Standard on carbon dioxide extinguishing systems. NFPA 12, Section 1-5.2.2. National Fire Protection Association, 2000
(31) Propane. In: NIOSH pocket guide to chemical hazards. National Institute for Occupational Safety and Health, June 1997

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: 2005-02-15

Revision Indicators:
GHS Physical State 2005-08-19
Vapour pressure at 50 deg C 2006-01-17
Relative density 2006-09-28
Engineering controls 2006-11-15

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