Methane

Methane is a colourless, odourless, and extremely flammable gas that can be explosive when mixed with air. It is also called methyl hydride. Methane can be a liquid that needs to be refrigerated. Methane is emitted from several natural and human-related sources. The chemical formula for methane is CH4.Methane is the primary component of natural gas. Other natural sources of methane include permafrost, termites, oceans, bodies of fresh water, wildfires, mud volcanoes, decaying matter in wetlands, digestive processes of animals, and underground and underwater deposits of methane called methane clathrates.[fusion_builder_container hundred_percent=”yes” overflow=”visible”][fusion_builder_row][fusion_builder_column type=”1_1″ background_position=”left top” background_color=”” border_size=”” border_color=”” border_style=”solid” spacing=”yes” background_image=”” background_repeat=”no-repeat” padding=”” margin_top=”0px” margin_bottom=”0px” class=”” id=”” animation_type=”” animation_speed=”0.3″ animation_direction=”left” hide_on_mobile=”no” center_content=”no” min_height=”none”][1]

Uses [2]

  • Methane is used in industrial chemical processes and may be transported as a refrigerated liquid (liquefied natural gas, or LNG).
  • Gas pipelines distribute large amounts of natural gas, of which methane is the principal component.
  • Methane is important for electrical generation by burning it as a fuel in a gas turbine or steam boiler.
  • Methane in the form of compressed natural gas is used as a vehicle fuel and is claimed to be more environmentally friendly than other fossil fuels such as gasoline/petrol and diesel.
  • Liquefied natural gas or LNG is natural gas (predominantly methane, CH4) that has been converted to liquid form for ease of storage or transport.
  • In a highly refined form, liquid methane has been investigated as a rocket fuel.
  • In the chemical industry, methane is converted to synthesis gas, a mixture of carbon monoxide and hydrogen, by steam reforming.
  • Related chemistries are exploited in the Haber-Bosch Synthesis of ammonia from air, which is reduced with natural gas to a mixture of carbon dioxide, water, and ammonia.
  • Methane is also subjected to free-radical chlorination in the production of chloromethanes, although methanol is a more typical precursor.

Sources & Routes of Exposure

Sources of Exposure [3]

  • Breathing: Most exposures occur when people inhale methane. Methane can go into homes through sewer traps or foundation cracks. People can be exposed by inhaling the chemical at work, cooking on a gas stove, or entering confined spaces such as manholes, silos, animal waste pits, septic tanks and sewers.
  • Drinking/Eating: Because methane evaporates quickly, it is usually not found in food or drinking water. Very low-level exposure can occur when contaminated water is used for drinking and/or for food preparation or when children eat contaminated soil.
  • Touching: Methane gas does not pass readily through intact skin. Methane in its extremely cold liquefied form can, however, cause burns to the skin and eyes.

Routes of Exposure [4]

The main routes of exposure to methane are via inhalation and contact with skin and/or eyes.

Health Effects [4]

Acute Effects

  • Inhalation: Low concentrations are not harmful. A high concentration can displace oxygen in the air. If less oxygen is available to breathe, symptoms such as rapid breathing, rapid heart rate, clumsiness, emotional upsets and fatigue can result. As less oxygen becomes available, nausea and vomiting, collapse, convulsions, coma and death can occur. Symptoms occur more quickly with physical effort. Lack of oxygen can cause permanent damage to organs including the brain and heart.
  • Skin Contact: Not irritating. Direct contact with the liquefied gas can chill or freeze the skin (frostbite). Symptoms of mild frostbite include numbness, prickling and itching. Symptoms of more severe frostbite include a burning sensation and stiffness. The skin may become waxy white or yellow. Blistering, tissue death and infection may develop in severe cases.
  • Eye Contact: Not irritating. Direct contact with the liquefied gas can freeze the eye. Permanent eye damage or blindness can result.
  • Ingestion: Not a relevant route of exposure (gas).

Chronic Effects

  • Methane has no ongoing harmful effects.

Cancer Risk

  • Methane is not a carcinogen.

Safety [4]

First Aid Measures

  • Inhalation: Take precautions to prevent a fire (e.g. remove sources of ignition). In case of oxygen deficiency: take precautions to ensure your own safety before attempting rescue (e.g. wear appropriate protective equipment). Move victim to fresh air. Keep at rest in a position comfortable for breathing. If breathing is difficult, trained personnel should administer emergency oxygen. If the heart has stopped, trained personnel should start cardiopulmonary resuscitation (CPR) or automated external defibrillation (AED). Immediately call a Poison Centre or doctor. Treatment is urgently required. Transport to a hospital.
  • Skin Contact: Not applicable (gas). Liquefied gas: quickly remove victim from source of contamination. DO NOT attempt to rewarm the affected area on site. DO NOT rub area or apply direct heat. Gently remove clothing or jewellery 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 victim to drink alcohol or smoke. Immediately call a Poison Centre or doctor. Treatment is urgently required. Transport to a hospital.
  • Eye Contact: Not applicable (gas). Liquefied gas: 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 call a Poison Centre or doctor. Treatment is urgently required. Transport to a hospital.
  • Ingestion: Not applicable (gas).

Fire Hazards & Extinguishing Media

  • Flammable Properties: Methane is a flammable gas, which can easily ignite. In addition, it can readily form explosive mixture with air at room temperature and may be ignited by static discharge.
  • Suitable Extinguishing Media: Dry chemical powder and high-expansion foam. Foam manufacturers should be consulted for recommendations regarding types of foams and application rates.
  • Unsuitable Extinguishing Media: DO NOT use carbon dioxide, low expansion foams, and direct application of water on liquefied gas.

Specific Hazards for Methane

  • Gas or vapour may travel a considerable distance to a source of ignition and flash back to a leak or open container.
  • Gas or vapour may accumulate in hazardous amounts in low-lying areas especially inside confined spaces, resulting in a health hazard. Methane can displace oxygen in the air, causing suffocation.
  • Direct addition of water to liquefied gas will cause flash vaporisation resulting in an explosion (either immediately or delayed) known as a “boiling liquid, expanding vapour explosion (BLEVE)”.
  • Heat from fire can cause a rapid build-up of pressure inside cylinders. Explosive rupture and a sudden release of large amounts of gas may result. Cylinder may rocket.
  • In a fire, the following hazardous materials may be generated: very toxic carbon monoxide, carbon dioxide.

Engineering Controls

  • Use local exhaust ventilation, if general ventilation is not adequate to control amount in the air.
  • Use non-sparking ventilation systems, approved explosion-proof equipment and intrinsically safe electrical systems in areas where this product is used and stored.
  • Do not allow product to accumulate in the air in work or storage areas, or in confined spaces.
  • For large-scale use of this product: use stringent control measures such as process enclosure to prevent product release into the workplace.

Personal Protective Equipment

The following personal protective equipment is needed when working with methane:

  • Eye/Face Protection: Wear chemical safety goggles and face shield when contact is possible.
  • Skin Protection: Always wear insulated protective clothing, if contact with refrigerated gas is possible. For cryogenic liquids, materials include: Tychem® Responder.
  • Respiratory Protection: Not normally required. If the oxygen content of the air is below acceptable limits, wear a NIOSH approved self-contained breathing apparatus (SCBA) or supplied air respirator.

Regulations

United States

  • ACGIH: The American Conference of Industrial Hygienists has set a threshold limit value (TLV) for methane of 1000ppm over an 8-hour workshift.

References

http://toxtown.nlm.nih.gov/text_version/chemicals.php?id=92

http://en.wikipedia.org/wiki/Methane

http://www.dhs.wisconsin.gov/eh/chemfs/fs/Methane.htm

http://www.ccohs.ca/oshanswers/chemicals/chem_profiles/methane.html

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