Seriously when was the last time you worker, other than maybe people working in the brownfields covered methane gas and risks at work. And where you might or will find it and what risks it can impose on our staff. I recently viewed a college post on Linkedin video where a normal person drops something flammable down a man hole and the reaction was the street exploded in flame blowing the man hole cover off into the air, most of use would say NO DAH!, but that because we are trained right! So for us who are trained dont read the following because you are COMPETENT under the act and legislation, but for everyone else here is the knowledge your supervisors should be looking at regarding Methane safety and you!
Methane (CH4) is a colorless, odorless, tasteless, flammable gas that is widely distributed in nature. Methane Gas is produced whenever organic material is decomposed by bacterial action in the absence of oxygen. The atmosphere contains about 2.2 ppm by volume of Methane.
In addition to methane (CH4) and carbon dioxide (CO2), numerous trace gases may be present in ground gas, depending on the material that is decomposing. Trace constituents principally may include carbon monoxide (CO) and hydrogen sulphide (H2S). However, in addition, but to a lesser extent, the following compounds may also be present: • Alcohols (CnH2n+1OH); • Alkanes (CnH2n+2), cycloalkanes (CnH2n) and alkenes (CnH2n); • Aromatic hydrocarbons (monocyclic or polycyclic); • Esters (e.g. methyl formate, H-COO-CH3) and ethers (e.g. ethoxyethane, CH3- CH2-O-CH2-CH3); • Halogenated compounds; and • Organosulphur compounds and mercaptans (also called ‘thiols’, where the compound contains the functional group -SH).
At room temperature and standard pressure, methane is a colorless, odorless gas. The familiar smell of natural gas as used in homes is achieved by the addition of an odorant, usually blends containing tert-butylthiol, as a safety measure. Methane has a boiling point of −161 °C (−257.8 °F) at a pressure of one atmosphere. As a gas it is flammable over a range of concentrations (4.4–17%) in air at standard pressure.
Solid methane exists in several modifications. Presently nine are known. Cooling methane at normal pressure results in the formation of methane I. This substance crystallizes in the cubic system (space group Fm3m). The positions of the hydrogen atoms are not fixed in methane I, i.e. methane molecules may rotate freely
Asphyxiant Properties Although methane is considered to be of low toxicity, its capability to displace oxygen means that at high enough concentrations it becomes an asphyxiant. Oxygen starvation occurs at 33%v/v methane, whilst at 75%v/v methane death results after 10 minutes. Carbon dioxide is an asphyxiant and poses a risk to humans as it excludes oxygen. The density of carbon dioxide means that it can collect in poorly ventilated spaces such as inspection pits and excavations. Concentrations of 6%v/v t0 10%v/v can produce unconsciousness or death in less than 15 minutes.
Methane Gas Entry into Homes and Commercial Buildings
Like Radon, Methane gas can migrate significant distances under the ground surface and be forced into adjacent buildings by the pressure gradient between the soil and the building interior. Points of entry include floor/wall cracks, floor drains, sewer pipe entry points as well as utility access penetrations. Gas can accumulate inside wall cavities, crawl spaces, and inside sumps and poorly ventilated basement areas. Methane and carbon dioxide do not have odours themselves. However, numerous trace constituents within ground gas can be odorous, with hydrogen sulphide being of most note with a smell of rotten eggs. The presence of an odour may increase the perception of adverse health effects being associated with a development. Effects on Vegetation Vegetation dieback has been correlated with the presence of ground gases. This is thought to be a result of carbon dioxide causing toxic reactions in the roots, whilst oxygen deficiency caused by the presence of methane and/or carbon dioxide can occur.
Gas Solubility The solubility of a gas has an impact on the concentration of that gas that will be emitted from the ground. The solubility of gases increases with pressure, meaning that at higher barometric pressures, measured concentrations of gas in the ground may be lower, as more of the gas will be dissolved in water. Temperature also has an impact on gas solubility, with solubilities of gases generally increasing as temperatures decrease. Methane can be transported as a dissolved product in groundwater (although solubility is very low), as well as moving through the subsurface in gaseous form. Once in the atmosphere, it will break down in anywhere from nine to 15 years as it is exposed to oxygen and water vapor.
BUT NOT ALWAYS
SOURCES OF GROUND GASES Methane is produced from both man-made (anthropogenic) and natural sources. Anthropogenic sources include landfilling activities, decomposition of organic material in made ground, natural gas pipelines and coal mines. Natural methane sources include coal measures deposits and marshland. As for methane, carbon dioxide has both anthropogenic and natural sources. Decomposition of waste materials with a small organic material content results in the production of carbon dioxide alongside methane. Carbon dioxide may be generated naturally in areas of chalk and limestone by the action of acidic rainwater. As methane is biochemically reactive, it is generally readily oxidised to carbon dioxide under aerobic conditions. Carbon dioxide, therefore, is often associated with the presence of methane.
Methane Toxicity: Fire/Explosion Risk
Methane gas is relatively non-toxic; it does not have an OSHA PEL Standard. Its health affects are associated with being a simple asphyxiant displacing oxygen in the lungs. Miners previously placed canaries in deep mines to check methane gas levels. Reportedly, canaries keeled over at about 16% oxygen indicating it was time to leave.
Methane is extremely flammable and can explode at concentrations between 5% (lower explosive limit) and 15% (upper explosive limit). These concentrations are much lower than the concentrations at which asphyxiant risk is significant. Reportedly, the most violent methane explosions occur at concentrations of about 9%; coal mines are hence kept well ventilated (pumped with fresh air) to maintain methane levels at or below 1%. Methane is synthesized commercially by the distillation of bituminous coal and by heating a mixture of carbon and hydrogen. It can be produced in the laboratory by heating sodium acetate with sodium hydroxide and by the reaction of aluminum carbide (Al4C3) with water.
In the chemical industry, methane is a raw material for the manufacture of methanol (CH3OH), formaldehyde (CH2O), nitromethane (CH3NO2), chloroform (CH3Cl), carbon tetrachloride (CCl4), and some freons (compounds containing carbon and fluorine, and perhaps chlorine and hydrogen). The reactions of methane with chlorine and fluorine are triggered by light. When exposed to bright visible light, mixtures of methane with chlorine or fluorine react explosively.
Methane gas is lighter than air and the highest concentrations inside buildings are found near the ceiling. The Methane detector should be installed no closer than 6 inches from the ceiling and away from dead air spaces such as corners.
Conversely, propane gas is heavier than air and accordingly will sink and accumulate at floor level. Propane gas detectors should be placedon the wall 2 feet from the floor and at least 2 feet from any corner.
Carbon monoxide is about 3% lighter than air and at normal room temperature will disperse uniformly in all directions throughout the room.Install your CO alarms within 40 feet of all rooms used for sleeping purposes, especially near furnaces, hot water heaters, fire places, etc.