Mines Gases-Oxygen Percentage|Damps|Degree of Seam

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Know About Mines Gases

We know that is necessary of air to take breath.As we go inside the mine,the primary importance is ventilation which means "the atmospheric air go inside the mine and by clearing impurities come out side".
The general composition of air in the atmosphere is as follow
1.By Volume
Oxygen-20.95%
Nitrogen-78.09%
Carbon dioxide-0.03%
Other rare gases(including Argon)-0.93%
Or less than 1%
2.By Weight
Oxygen-23.15%
Nitrogen-75.52%
Carbon dioxide-0.046%
Other rare gases(Including argon)-1.3%(approx.).
:- Gassy Coal Mine (degree 2 and 3)
 *In return air the constituents should be
Oxygen-20.28
Nitrogen-78.90
Carbon monoxide-0.36
Methane-0.46

 As the gases passes through the Mine environment many impurities mixed with the composition mentioned above and also the percentage of Oxygen reduces due combustion, spontaneous heating and human breathing.

DAMP 
In mines the miner faces great difficulties due to damp.We can define damp as "the impurities present and also harmful for working in Mine".
The word damp means fog,smog,fumes or vapour.
Mainly the following damps are present in Mine...
1.Fire Damp:-The word fire dam is synonyms of Methane(CH4) and Mars gas.
The exploitative percentage of Methane is between 5.4 to 14.8 with respect to Oxygen.
*For the human survivability the minimum percentage of Oxygen should be 15.

 2.Black Damp:-It is the mixture of Nitrogen and Carbon dioxide.
The Black damp is also called Chock damp.

3.White Damp:-It is the mixture of Carbon monoxide and air.
Source:-Emission from strata,Diesel  engine etc.

4.Stink Damp:-It is the mixture of air and hydrogen sulphide.

5.After Damp:-It is the mixture of many impurities in the U/G atmosphere after the fire damp or Coal dust explosion.

Degrees of Seam
1.The seam in which the emission of fire damp is not more than one cubic meter per tonne of coal and the percentage of methane emission should be less than 0.1%(in general air). The seam called first degree.

2.The seam in which the emission of Fire damp is between one to ten cubic meter per tonne of coal production and the percentage of emission should be more than 0.1%(in general air).The seam second degree.

3.The seam,called third degree when the Fire damp emission is more than ten cubic meter/tonne of coal production.

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