JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II MINE ENVIRONMENTAL ENGINEERING - I Previous Question Paper (April - 2018 - R16)

In underground coal mines, NOx fumes (primarily NO and NO2) originate mainly from the detonation of explosives, particularly when blasting is incomplete or involves low-quality or damp explosives. They also occur as a byproduct of diesel engine exhaust from underground machinery and, to a lesser extent, from the spontaneous combustion of coal or high-temperature oxidation processes. These gases typically accumulate in poorly ventilated headings, dead-ends, or areas immediately following blasting operations where dilution by the main ventilation current is restricted.

A third degree of gassy mine is a coal mine where the rate of emission of inflammable gas exceeds 10 cubic metres per tonne of coal raised. Alternatively, it is classified as such if the percentage of inflammable gas in the general body of the return air exceeds 0.5 percent. These mines are considered highly hazardous due to the significant risk of methane accumulation, requiring stringent ventilation standards and the use of intrinsically safe electrical equipment.