What is the required size of rock dust for compliance?

The required size of rock dust for compliance is that all material must pass through a twenty (20) mesh screen. This size specification is established to ensure that the rock dust is fine enough to effectively suppress coal dust explosions and provide adequate coverage on the surfaces of the mine. The finer particles can settle and adhere to surfaces, creating a barrier that inhibits the rapid propagation of fire and explosion, which is critical for maintaining safety in underground mining operations.

Using a twenty mesh screen ensures a balance between efficiency in dust management and the physical properties necessary to achieve effective dust suppression. Finer dust can be more easily spread and distributed within the mine environment, which enhances its performance as a dust suppressant. If the particles were coarser, they might not achieve the desired protective effect, as they could fail to fill in the smaller voids where explosive dust can accumulate.