When can a coal dust explosion be most likely to occur?

A coal dust explosion is most likely to occur when particles are suspended in the air and there is a source of ignition, such as a flame or spark. This is because the fine coal dust particles can become airborne and form a cloud that can ignite if it comes into contact with a sufficient heat source. When properly dispersed, coal dust creates an explosive mixture with air that can ignite and lead to a rapid combustion reaction, resulting in an explosion.

The presence of a flame or spark is critical, as it provides the necessary energy to initiate the combustion of the coal dust cloud, culminating in a potentially catastrophic explosion if not controlled. Understanding the conditions under which coal dust can explode is essential for maintaining safety in underground mining operations.