What is the lower explosive limit of a gas detector?
For a combustible gas tester, there is no danger when the concentration of the combustible gas is either too low or too high. It will only burn or explode when it mixes with air to form a gas mixture, or more precisely, when it forms a gas mixture with oxygen in a certain proportion. Combustion is an intense oxidation reaction accompanied by light and heat. It must have three elements: a. Combustible substance (gas); b. Combustion-supporting substance (oxygen); c. Ignition source (temperature). The combustion of combustible gases can be divided into two categories. One is diffusion combustion, that is, the volatilized or ejected and leaked combustible gas from equipment burns when it meets an ignition source and mixes. The other type of combustion is the combustion of a mixture of combustible gas and air when it catches fire. This kind of combustion reaction is intense and rapid, generally generating great pressure and sound, and is also called an explosion. There is no strict distinction between combustion and explosion.
Relevant authoritative departments and experts have conducted combustion and explosion analyses on the currently discovered combustible gases and formulated the explosion limits of combustible gases, which are divided into the upper explosive limit (abbreviated as UEL, the abbreviation of the English "upper explode limit") and the lower explosive limit (abbreviated as LEL, the abbreviation of the English "lower explode limit"). Below the lower explosive limit, the content of the combustible gas in the gas mixture is insufficient to cause combustion or explosion. Above the upper explosive limit, the content of oxygen in the gas mixture is insufficient, and it also cannot cause combustion or explosion. In addition, the combustion and explosion of combustible gases are also related to factors such as gas pressure, temperature, and ignition energy. The explosion limit is generally expressed as a volume percentage concentration.
The explosion limit is the general term for the lower explosive limit and the upper explosive limit. A combustible gas will only explode when its concentration in the air is between the lower explosive limit and the upper explosive limit. There will be no explosion when it is below the lower explosive limit or above the upper explosive limit. Therefore, when conducting explosion measurements, the alarm concentration is generally set below 25% LEL of the lower explosive limit.
