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(1) Gas rank of the mine
     According to the "Safety Regulations for Coal Mines") (hereinafter referred to as "Procedures)), according to the mine's relative gas emission, absolute gas emission and gas emission, the mine gas grade is divided into three categories:
     1. Low gas mine. At the same time, the following conditions are met: the relative gas emission of the mine is ≤10m 3 /t, and the absolute gas emission of the mine is ≤ 40m 3 /min. The absolute gas emission of any mining face in the mine is ≤ 3 hours / t, any mining The absolute gas emission of coal working face is ≤ 5m 3 /t.
     2. High gas mine. The relative gas emission of the mine is >10m 3 /t, or the absolute gas emission of the mine is >40m 3 /min, or the absolute gas emission of any mining face in the mine is >3 hours/t, or any coal mining work in the mine. The absolute gas emission of the surface is >5m 3 /t.
     3. Highlight the mine
     The mine gas grade and carbon dioxide emission quantity must be identified every year, and reported to the provincial (autonomous region, municipality directly under the central government) for the approval of the coal industry management department, and reported to the provincial coal mine safety supervision agency for the record.
(2) Conditions for gas explosion
     A gas explosion occurs when the following three conditions are met:
     1) The concentration of gas in the air reaches 5%~16%;
     2) There must be a detonation source with a temperature of 650~7500C;
     3) The oxygen content in the air is not less than 12%.
Mine gas grade and explosion conditions
As long as there is a coal (rock) layer in a mine, gas is discovered, and the mine is a gas mine. Preventing and controlling coal and gas explosion construction is one of the important tasks of coal mine construction and production safety management.