Regarding the Detection Range of Gas Detectors and the Meaning of %LEL
LEL "refers to the lower explosive limit, which is a technical term for flammable gases. The minimum concentration of combustible gas that can explode when exposed to a spark in air is called the lower explosive limit, abbreviated as "LEL". English: Lower Explosion Limited.
The highest concentration of combustible gas that can explode when exposed to a spark in the air is called the upper limit of explosion, abbreviated as UEL. English: Upper Explosion Limited. The lower explosive limit (LEL) is an important indicator for combustible gas alarms and detectors. If the combustible gas in the environment is at the upper explosive limit or directly above the upper explosive limit, and the following three conditions are met, an explosion will occur. 1. Combustible material (gas); 2. Combustion aid (oxygen); 3 ignition sources (temperature). The alarm concentration is generally set below the lower explosive limit of "25% LEL". The measurement range of various combustible gas detectors produced by our company is "0-100% LEL". Fixed combustible gas detectors usually have two alarm points (the specific value depends on the model of the alarm host): "10% LEL" is the first level alarm, and "25% LEL" is the second level alarm. Portable combustible gas detectors usually have an alarm point: "25% LEL" is the alarm point. What exactly do "10% LEL" and "25% LEL" mean here? Let's give an example. For example, the lower explosive limit of methane is a "5%" volume ratio (i.e. when the volume content of methane in the air reaches 5%, it reaches the lower explosive limit). Divide this "5%" volume ratio into equal parts, and let the "5%" volume ratio correspond to "100% LEL". That is to say, when the detector value reaches the "100% LEL" alarm point, it is equivalent to the methane content being "5%" volume ratio at this time. When the value of the combustible gas detector reaches the "25% LEL" alarm point, it is equivalent to a methane content of "1.25%" by volume at this time.
So, you don't have to worry about whether there will be danger at any time after the combustible gas detector alarms, it is still a certain distance away from reaching an explosion. Take corresponding measures immediately, such as opening the exhaust fan, cutting off some valves, or opening the sprinkler system, so that the danger of explosion will not occur. There is still a long way to go before the lower explosive limit that may pose a real danger can be alerted, so as to serve as an alarm prompt.
