What is the required size of rock dust particles?

The correct answer is that all rock dust particles must pass through a 20 mesh screen, which indicates a specific size requirement for effective performance. In this context, a 20 mesh screen means that all particles must be small enough to fit through holes that are approximately 0.84 millimeters in diameter. Rock dust that meets this size specification is essential for ensuring proper dispersion in mines and enhancing the effectiveness of dust control measures.

Smaller particles are more effective at controlling dust and improving visibility, thereby contributing to safer working conditions. This size requirement also helps in minimizing the risk of ignition in the presence of combustible materials, as finer particles can better suppress the potential for coal dust explosions.

While passing through finer screens (larger mesh sizes) might seem beneficial, they could lead to a reduction in the efficacy of the dust suppression. Therefore, using rock dust that meets or falls below this specific mesh size is critical for achieving optimal safety and environmental conditions in mining operations.