What is a significant factor that can lead to explosion without methane?

The presence of coal dust raised in a dense cloud is a significant factor that can lead to explosions in underground mining environments, even in the absence of methane. When coal dust becomes airborne, particularly in a concentrated cloud, it can create a highly combustible mixture. The fine particles of coal dust have a large surface area that allows for rapid oxidation when ignited.

When a spark or heat source is introduced, the dust can ignite and cause a deflagration (a fast combustion process) that can quickly escalate into an explosion. This phenomenon is a well-documented risk in mining operations and is often monitored through dust control measures and regular safety protocols.

The other options do not present the same explosive potential when considered in isolation. The presence of water, for instance, can help suppress dust and reduce the likelihood of an explosion. Low temperature typically inhibits the ignition of combustible materials. While small particle size can contribute to the dust’s flammability, it is the dense cloud condition that is critical in the context of explosion risks. Thus, the specific characteristic of being densely suspended in the air is what makes coal dust a significant explosion risk in its own right.