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The limiting oxygen concentration is shown in the lower right of the diagram. 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 ...
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 upper and lower flammability limits of methane in air are located on this line, as shown (labelled UEL and LEL, respectively). The stoichiometric combustion of methane is: CH 4 + 2O 2 → CO 2 + 2H 2 O. The stoichiometric concentration of methane in oxygen is therefore 1/(1+2), which is 33 percent.
Oxygen levels around 20% — about the same concentration as in Earth's atmosphere — have been measured deep inside some of Berkeley's gas wells, indicating a leak or malfunction, according to ...
Methane is also an asphyxiant if the oxygen concentration is reduced to below about 16% by displacement, as most people can tolerate a reduction from 21% to 16% without ill effects. The concentration of methane at which asphyxiation risk becomes significant is much higher than the 5–15% concentration in a flammable or explosive mixture.
The lower flammability limit or lower explosive limit (LFL/LEL) represents the lowest air to fuel vapor concentration required for combustion to take place when ignited by an external source, for any particular chemical. [29] Any concentration lower than this could not produce a flame or result in combustion.
For each fuel, ignition occurs only within a certain range of concentration, known as the upper and lower flammability limits. For example, for methane and gasoline vapor, this range is 5-15% and 1.4-7.6% gas to air, respectively. An explosion can only occur when fuel concentration is within these limits [citation needed]
The flammability limits of the gas define those proportions, i.e. the ignitable range. In combustion engineering terms, the admission of inert gas can be said to dilute the oxygen below the limiting oxygen concentration. Inerting differs from purging. Purging, by definition, ensures that an ignitable mixture never forms. Inerting makes an ...