UPSC CSE Prelims 2000
Most mine explosions are caused by the ignition of methane gas mixed with air. Methane (CH₄) is a colorless, odorless gas naturally occurring in coal seams. When methane concentrations in the air reach between 5% and 15%, the mixture becomes highly explosive upon contact with an ignition source such as a spark, open flame, or hot surface. This phenomenon is a significant hazard in underground coal mining operations.
Hydrogen with oxygen: While a mixture of hydrogen (H₂) and oxygen (O₂) is highly explosive, hydrogen is not typically found in significant quantities in coal mines to cause widespread explosions. The primary combustible gas in mines is methane.
Oxygen with acetylene: Acetylene (C₂H₂) is a gas used in welding and cutting. It is not naturally present in coal mines, and therefore, its mixture with oxygen is not a cause of mine explosions.
Carbon dioxide with ethane: Carbon dioxide (CO₂) is a non-combustible gas and acts as a fire suppressant. Ethane (C₂H₆) is a combustible hydrocarbon, but it is typically present in much smaller quantities than methane in coal mines and is not the primary cause of large-scale mine explosions. The mixture of CO₂ with any combustible gas would generally reduce its flammability.