What dangerous gas may be formed when water is applied to a mine fire?

When water is applied to a mine fire, the reaction can produce water gas, which is a mixture of carbon monoxide (CO) and hydrogen (H2). This occurs primarily because the extreme heat from the fire can react with the water, resulting in a gas that can be highly flammable and dangerous if ignited. Water gas can significantly increase the risks associated with the fire, as both components are toxic and can lead to hazardous conditions for miners.

In the context of the other gases presented, while carbon dioxide and methane are common in mine environments, they do not arise primarily from the application of water to a fire. Hydrogen sulfide, another potentially dangerous gas found in mines, is also not a direct result of this interaction. Thus, the specific formation of water gas (CO and H2) as a consequence of water being applied to a mine fire makes this choice the most accurate and relevant in terms of understanding the hazards present during firefighting efforts in mining operations.