What does combustible gas detector lel mean?
The minimum content of flammable gas that can cause an explosion is called the Lower Explosion Limit (LEL). LEL is not a unit, it refers to a numerical value, which generally refers to the volume ratio of explosive gases in the air. The value of LEL is not detected by instruments. It has different values for different gases in national standards.
The data displayed by the gas detection instrument only indicates the concentration of flammable gases in the air to serve as an alarm. Generally, quantitative analysis instruments have labels indicating what gases they are detecting. If it is a qualitative analysis instrument, it cannot show what kind of gas it is.
The highest concentration of combustible gas that explodes when encountering an open fire in the air is called the upper explosion limit - or "UEL" for short. English: Upper Explosion Limited.
The lower explosion limit LEL is an important indicator of combustible gas alarms and combustible gas detectors. If flammable gases in the environment are explosive
Between the lower limit and the upper limit of explosion, and the following three conditions are met, an explosion will occur. 1. Combustible material (gas); 2. Combustion-supporting material (oxygen); 3. Ignition source (temperature). The alarm concentration is generally set below the "25% LEL" of the lower explosion limit.
Fixed combustible gas detectors usually have two alarm points (the specific value is related to the model of the alarm host): "10% LEL" is a first-level alarm, and "25% LEL" is a second-level alarm. Portable combustible gas detectors usually have an alarm point: "25% LEL" is the alarm point.
So what do "10%LEL" and "25%LEL" here mean?
Let us give an example. For example, the lower explosion limit of methane is "5%" volume ratio (that is, the lower explosion limit is reached when the volume content of methane in the air reaches 5%). Divide this "5%" volume ratio into one hundred equal parts, let "5%" volume ratio corresponds to "100%LEL".
That is to say, when the detector value reaches the "100% LEL" alarm point, it is equivalent to the methane content at this time being "5%" volume ratio. When the combustible gas detector value reaches the "25% LEL" alarm point, it is equivalent to the methane content at this time being "1.25%" volume ratio.
Therefore, there is no need to worry about whether the combustible gas detector will be in danger at any time after the alarm. It is still a certain distance away from explosion. If appropriate measures are taken immediately, such as turning on the exhaust fan or cutting off some valves or turning on the sprinkler system, the risk of explosion will not occur. There is still a long way to go before the lower limit of explosion where danger may occur. Only in this way can the alarm be played.
