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The term is considered by many safety professionals to be the same as the lower explosive level (LEL). At a concentration in air lower than the LFL, gas mixtures are "too lean" to burn. Methane gas has an LFL of 4.4%. [1] If the atmosphere has less than 4.4% methane, an explosion cannot occur even if a source of ignition is present.
The limiting oxygen concentration (LOC), [1] also known as the minimum oxygen concentration (MOC), [2] is defined as the limiting concentration of oxygen below which combustion is not possible, independent of the concentration of fuel. It is expressed in units of volume percent of oxygen. The LOC varies with pressure and temperature.
Consider the first triangular diagram below, which shows all possible mixtures of methane, oxygen and nitrogen. Air is a mixture of about 21 volume percent oxygen, and 79 volume percent inerts (nitrogen). Any mixture of methane and air will therefore lie on the straight line between pure methane and pure air – this is shown as the blue air-line.
Compared to liquid hydrogen, the specific energy of methane is lower but this disadvantage is offset by methane's greater density and temperature range, allowing for smaller and lighter tankage for a given fuel mass. Liquid methane has a temperature range (91–112 K) nearly compatible with liquid oxygen (54–90 K).
The lower flammability limit (LFL), [1] usually expressed in volume per cent, is the lower end of the concentration range over which a flammable mixture of gas or vapour in air can be ignited at a given temperature and pressure. The flammability range is delineated by the upper and lower flammability limits. Outside this range of air/vapor ...
The Bay Area Air Quality Management District has fined Berkeley after finding explosive levels of methane leaking from at least two cracked gas collection wells in the park. Both have since been ...
Liquid properties Std enthalpy change of formation, Δ f H o liquid? kJ/mol Standard molar entropy, S o liquid? J/(mol K) Heat capacity, c p? J/(mol K) Gas properties Std enthalpy change of formation, Δ f H o gas: −74.6 kJ/mol [8] Standard molar entropy, S o gas: 186.3 J/(mol K) [8] Enthalpy of combustion Δ c H o: −802 kJ/mol [9] Heat ...
Those measures usually include barriers across roads and sidewalks − cities often use trash trucks or snowplows − along with jersey barriers to create an s-shaped approach to limit vehicles ...