Nowadays, with the occurrence of various explosion news caused by gas leakage, it has been clearly stipulated in relevant laws and regulations that if production and business units in catering and other industries use gas, they should install combustible gas alarm devices and ensure their normal use. The use of combustible gas alarm can quickly and accurately detect the concentration of combustible gas and display the real-time concentration value on the spot. When the concentration of combustible gas reaches the alarm value set by the alarm, it will send out an audible and visual alarm signal. What is the concentration of combustible gas alarm ? The following is a brief introduction by yi yun Tian:

according to article 5.5" measurement "in GBT 50493-2019 petrochemical combustible gas and toxic gas detection alarm design standard range and alarm value setting:

1. The primary alarm setting value for combustible gas should be less than or equal to 25% LEL.

2. The secondary alarm setting value for combustible gas should be less than or equal to 50% LEL.

3. the primary alarm setting value for linear combustible gas measurement shall be 1LEL · m; The secondary alarm setting value shall be 2LEL · m.

where LEL is the English lower explosion The abbreviation of limit refers to the lowest concentration at which a mixture of combustible vapor, gas or dust and air can explode when exposed to an ignition source (the concentration of combustible vapor and gas, calculated by volume ratio).

The concentration of combustible gas is too low or too high. It is not dangerous. It can only be mixed with air to form a mixed gas or more precisely When it meets oxygen to form a certain proportion of mixed gas, it will burn or explode.Due to the higher proportion of air, when monitoring the leakage concentration of combustible gas, it is necessary to monitor the volume concentration value from very low concentration to the lowest explosion limit, that is, the measurement range is 0~100 LEL.

the concentration alarm value of combustible gas is generally preset in the instrument. according to the provisions in the national standard, the first-level alarm setting value of combustible gas is not higher than the minimum explosion limit of 25% LEL. Therefore, the alarm value of the gas alarm specified in the national code is the upper limit, as long as it is not greater than this upper limit, it is within a reasonable range. Of course, from a professional practical point of view, the combustible gas alarm value should not be too low, too low prone to false positives, because too low may conflict with the detection error. As for the specific minimum limit for the explosive concentration of each combustible gas, it can be referred to the GBT Appendix A in 50493-2019: Characteristics of Common Flammable Gases and Vapors. There are not only upper and lower limits of explosive concentration (V%) of common flammable gases and vapors, but also parameters such as boiling point, flash point and vapor density.