Â· 43 comments. in Facts. An intelligence quotient, or IQ, is a score derived from one of several standardized tests designed to assess intelligence. The abbreviation âIQâ comes from the German term Intelligenz-Quotient, originally coined by psychologist William Stern.
Lower explosive limit. Lower explosive limit (LEL): The lowest concentration (percentage) of a gas or a vapor in air capable of producing a flash of fire in presence of an ignition source (arc, flame, heat). The term is considered by many safety professionals to be the same as the lower flammable limit (LFL).
At a concentration in air lower than the LEL, gas mixtures are too lean to burn. Methane gas has an LEL of 4.4%. If the atmosphere has less than 4.4% methane, an explosion cannot occur even if a source of ignition is present.Percentage reading on combustible air monitors should not be confused with the LEL concentrations.pper explosive limit (UEL): Highest concentration (percentage) of a gas or a vapor in air capable of producing a flash of fire in presence of an ignition source (arc, flame, heat). Concentrations higher than UFL or UEL are too rich to burn.