Methane (CH4) is a naturally occurring hydrocarbon that is colorless, odorless and tasteless. Methane is the chief constituent of natural gas, and high concentrations of the gas can cause oxygen-deficient atmospheres, flammable situations, or explosive environments. Potential sources of methane gas, also referred to as natural gas, fire-damp, and marsh gas, include: coal seams, oil and gas formations, organic rich shale formations, and environ–ments with decaying organic matter such as landfills and swamps.


Sources of impurity: Owners of wells containing methane frequently hear gur–gling or bubbling noises coming from their wells. Other signs might be effervescent gas bubbles in water drawn from a faucet or sounds similar to that of boiling water coming from your plumbing. Not all gas released from well water is methane, but caution should be practiced until the gas is identified. When signs of methane are present, it is recommended that any confined spaces in areas where high water usage is occurring, such as laun–dry rooms, bathrooms or kitchens, be well ventilated until further investigations are made to determine whether methane is indeed present in the well water.


Additional notes from Canadian government:



Maine Maximum Exposure Guideline limit:

USA Primary Drinking Water Standard limit:

USA Secondary Drinking Water Standard limit:

Canada Health standard limit:

Canada Aesthetic standard limit:

USA daily recommended allowance:

Other standard: Federal and state drinking-water quality standards do not establish limits for methane in water wells. However, given the hazardous nature of methane in water wells, the U.S. Department of the Interior, Office of Surface Mining (Eltschlager and others, 2001) recommends the following: ● Owners of wells with dissolved methane concentrations greater than 28 mg/L should immediately contact their county health department to obtain assistance and guidance in venting the wellhead and for other possible remediation alternatives. Owners of wells with methane concentrations greater than 10 mg/L but less than 28 mg/L may also wish to contact their local county health department for further assistance and consider removing potential ignition sources from the immediate area. ● Methane concentrations less than 10 mg/L require no action, other than periodic monitoring to see if methane concentrations are changing.


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