"LEL" refers to the lower limit of explosion. The minimum concentration of flammable gas in the air when it encounters an open flame is called the lower explosion limit - abbreviated as %LEL. English: Lower Explosion Limited.
The highest concentration of flammable gas explosion in the air when encountered by an open flame is called the upper limit of explosion - abbreviated as %UEL. English: Upper Explosion Limited.
So what is the lower explosion limit?
There is no danger in the concentration of combustible gases that are too low or too high, and it will only burn or explode if it mixes with air to form a mixture, or rather oxygen, to form a certain proportion of the mixture. Combustion is an intense oxidation reaction accompanied by luminous heat, which must have three elements: a. Combustible materials (gas); b. Oxygen; c. Ignition source (temperature). The combustion of flammable gas can be divided into two categories, one is diffusion combustion, that is, volatile or ejected and leaking flammable gas from the equipment, and mixed combustion when encountering the ignition source. Another type of combustion is flammable gas mixed with air to burn, which reacts violently and quickly, generally producing huge pressure and sound, also known as explosion. There is no strict distinction between combustion and explosion.
Relevant authorities and experts have conducted a combustion explosion analysis of the flammable gas found so far, and formulated the explosion limit of combustible gas, which is divided into upper explode limit (English upper explode limit abbreviated UEL) and lower explosion limit (English lower explode limit abbreviated LEL?). Below the lower explosion limit, the content of flammable gas in the mixture is insufficient to cause combustion or explosion, and the content of oxygen in the mixture above the upper limit is insufficient, nor can it cause combustion or explosion. In addition, the combustion and explosion of flammable gas are also related to the pressure, temperature, ignition energy and other factors of the gas. The explosion limit is generally expressed as a percentage concentration by volume.
The explosion limit is a general term for the lower explosion limit and the upper explosion limit, and the concentration of flammable gas in the air will only explode between the lower explosion limit and the upper explosion limit. No explosion will occur below or above the lower explosion limit. Therefore, when conducting explosion measurements, the alarm concentration is generally set below 25% LEL of the lower explosion limit.
The various Flammable gas detectors produced by our company have a measurement range of 0-100% LEL.
fixedFlammable gas detectors usually have two alarm points (depending on the model of the alarm host): 10% LEL for Level 1 alarm and 25% LEL for Level 2 alarm.
PortableFlammable gas detectors usually have an alarm point: 25% LEL is the alarm point.
For example, the lower explosion limit of methane is 5% volume ratio, that is, divide this 5% volume ratio into 100% equal parts, so that the 5% volume ratio corresponds to 100% LEL, that is, when the detector value reaches the 10% LEL alarm point, it is equivalent to the content of methane at this time is 0.5% volume ratio. When the detector value reaches the 25% LEL alarm point, it is equivalent to the content of methane at this time is 1.25% volume ratio.
Therefore, you don't have to worry about whether there is danger at any time after the alarm, at this time it is reminding you to take corresponding measures immediately, such as opening the exhaust fan or cutting off some valves, etc., there is still a big gap from the lower limit of the explosion that is really dangerous, so that it will play the role of alarm reminder.