How far must rock dust be applied in relation to the last open crosscut?

The correct answer indicates that rock dust must be applied to within forty (40) feet of the face in an underground mine. This requirement is essential for maintaining safety and reducing the risk of coal dust explosions. Coal dust can ignite and cause catastrophic events if proper precautions aren't taken. Applying rock dust helps to suppress coal dust and provides a barrier that mitigates the potential for explosions.

The specific distance of forty feet is determined by safety regulations that take into account both the effectiveness of rock dust in reducing the flammability of coal dust and the practicalities of operations within the mine. Ensuring that the rock dust is applied within this specified distance helps create a safer working environment for miners and reduces the likelihood of hazardous incidents occurring. It is crucial for mine foremen to adhere to these guidelines in order to maintain compliance with safety standards and protect the health of all personnel underground.