Methane gas is primarily a greenhouse gas, and causes negative effects in the atmosphere. However, there are also many places in which an individual may come into contact with methane gas. It is a colorless, odorless gas, so any methane present may not be immediately noticeable. Commercial methane may have an odorant added for safety purposes. It is a Class A (Compressed Gas) and Class B1 (Flammable Gas) chemical.
HUMAN RELATED SOURCES
Humans create sources of methane primarily through the burning of fossil fuels. Methane emissions can come from commercial vehicles, equipment operation in factories and oil fields, and the processing and storing of natural gas. Two of the most dangerous sources of methane emissions are from hydraulic fracking, where methane can leak into groundwater and affect the surrounding environment, and coal mining, where methane deposits become trapped underground and can cause fires or explosions.
HOW TO AVOID METHANE
Everyone inhales small amounts of methane everyday, and that is unavoidable. However, in certain areas, methane accumulation can become dangerous and it is important to know how to avoid coming in contact with large quantities. Methane can accumulate in low-lying, confined spaces such as abandoned mine shafts. Exploring these spaces is not only dangerous due to the chance of becoming lost or injured, but also because of these deposits. An open flame could easily ignite the methane due to its flammable classification, and the safest means of extinguishing it is dry chemical powder or high-expansion foam. Water or typical extinguishers will not be effective. Methane also displaces oxygen in the air and inhaling large amounts can cause symptoms of oxygen deprivation. The most common areas for methane exposure are around farms, industrial sites, and the U.S. Southwest, because of the high number of human-related sources in that region. It is rare that one will become exposed to large amounts of methane, but being smart and avoiding known sources could help prevent illness or loss of life.
There are many naturally occurring sources of methane gas. The most well-known natural source is in the digestive processes of animals, primarily cows. It is also called marsh gas due to concentrations of methane gas in swamplands from decomposing material. There are also minor quantities of the gas in permafrost, oceans, fresh water, mud volcanoes, and wildfires. The most unique quantities of methane gas are found in underground deposits called methane clathrates, which were originally only thought to be found in the far reaches of the solar system, but have been found under sediment on the ocean floor.
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National Library of Medicine: Tox Town
Canadian Center for Occupational Health and Safety