How does the fineness of coal dust affect its explosibility?

The fineness of coal dust plays a critical role in its explosibility, and finer dust particles significantly increase the combustibility and explosibility of coal dust. When coal dust is finely divided, it can remain suspended in the air, creating an ideal mixture with oxygen. This enhances the surface area available for combustion, allowing for more rapid ignition and combustion.

Smaller particles can ignite more easily due to their increased surface area-to-volume ratio, meaning that more of the coal dust is available to react with the oxygen in the air. As a result, when a spark or flame is introduced, the increased surface area facilitates a faster and more intense combustion process, leading to the potential for an explosion.

Therefore, the correct understanding is that finer coal dust is more likely to lead to explosive conditions, increasing the risk of a dust explosion in underground mining environments. This emphasizes the importance of managing dust levels effectively to prevent hazardous conditions.