Methane: Health and Safety Hazards Fact Sheet

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Methane hazards can occur during manufacture, use, and transportation. Although we inhale methane in the air we breathe, exposure to high concentrations of methane is dangerous.
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Although naturally occurring in the atmosphere, methane is hazardous in high concentrations. Widely used in industrial processes, heating and electricity generation, methane can become a severe hazard if accidental release, leaks, or transportation incidents occur. Knowing what methane is, as well as its health and safety risks, is critical.

What is Methane?

Methane, or methyl hydride, is a colourless, odourless gas which is lighter than air. In the atmosphere, the gas is transformed into water and carbon dioxide; it is also one of the most potent greenhouse gases.

Methane is naturally emitted from the decomposition of organic matter and digestive process of ruminant animals; other sources include fossil fuel extraction, landfill, industrial process, food production and mining. It is commonly referred to as marsh gas, as it occurs abundantly in wetlands.

CAS Number: 74-82-8

Chemical Compound: CH4

Other names: fire damp, marsh gas, biogas, methyl hydride, carbane 

Chemical Properties

Molecular weight:                16.043 g/mol

Boiling point:                        -161°C

Melting point:                       -183°C

Relative vapour density (air = 1): 0.6

Auto-ignition temperature:  537°C

Safety Hazards of Methane

Methane hazards can occur during manufacture, use, and transportation. Although we inhale methane as we breathe, exposure to high concentrations of methane is dangerous.

Hazardous events occur due to accidents during transport, accidental releases at manufacturing facilities, and farming accidents. An in-depth emergency response plan and ongoing training are necessary to mitigate the risk of a crisis.

Methane in Mining

Methane is recovered from mines due to two main reasons, safety and energy production. Coal reserves are available in almost every country worldwide; the most significant reserves are in the USA, Russia, China and India.

Coal Mine Methane (CMM) is a blend of air and methane released from rock strata due to mining activities. Methane trapped within a coal seam emerges in a mine after removing layers of a coal face. Additionally, the gas can seep out of vents from abandoned mines or appear after a rock collapse from a post-mining area.

Due to its volatile nature, methane poses an extreme working hazard, requiring effective removal from the ventilation system. In some cases, further subtraction occurs through a series of wells, boreholes and pipelines, forming a degasification system (drainage system). Ventilation systems move the Methane contaminated air away from areas where personnel are working and into the shafts directed towards the surface. This air is captured and utilised in gas engines rather than pumped into the atmosphere due to its high greenhouses gas effect.

How to Monitor Methane Levels

Methane gas monitors feature a non-dispersive infrared (NDIR) sensor. Measurement is based on the physical property that CH4 molecules absorb infrared light or particular wavelengths. By shining light through the target gas and using suitable optical filters, the light detector gives an output that is converted into a CH4 concentration value.

The Aura-FX Methane Monitor measures CHlevels, ensuring it remains within a safe range. The sensor emits an initial warning signal at 1.1%, with an alarm sounding when levels reach 2.2%.

Methane Safety Regulation

NIOSH states, methane monitors are required by law to be mounted on machinery and throughout a mine to alert personnel of any increase in the gases levels while extracting coal.

Routine monitoring of methane is required at the working face of mine due to the higher propensity for ignition. Monitors are needed to provide alerts when levels exceed 1%. As levels can rise and fall rapidly, and personnel’s reaction times vary, there is a warning at 1% rather than the dangerous level of 5% to ensure an adequate and timely response.

The concentration of methane can occur away from the working face, which is often monitored less frequently. To ensure workers are continually protected, portable gas monitors need to be carried, reducing the risk to personnel moving across the site. The DMIRS specifically outlines maximum atmospheric levels of methane in the code of practice:

9.29. Monitoring of toxic, asphyxiant and explosive gases

(3) The manager of an underground mine must ensure that, in any workplace in that mine, the atmosphere does not contain more than 12500 ppm, or 1.25% by volume, of methane.

Mines Safety and Inspection Regulations 1995

Numerous gases associated with mining, tunnelling and underground construction are generalised into combustible, toxic and asphyxiate types. Because of the hazardous nature of these gases and the unique and restrictive structure of underground environments, these gases must be continuously monitored to mitigate risk.

Check out our other articles on hazardous gases including, carbon dioxidecarbon monoxide, and hydrogen sulfide.

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