What is a permissible pump?

A permissible pump refers specifically to a pump that has been approved for use in environments where there is a risk of explosive gases, such as return airways in underground mining operations. These pumps are designed and constructed to meet safety regulations and standards that allow them to operate in potentially hazardous areas without contributing to risks of ignition or explosion.

In the context of underground mining, ensuring that equipment such as pumps does not pose a danger to miners is crucial, especially in areas like return airways where air quality is critical for safety. Using a permissible pump in these areas helps maintain safe working conditions by effectively managing water and other materials without introducing additional hazards associated with equipment that is not specifically designed for such environments.

The other options listed do not align with the definition of a permissible pump. For example, pumps used for surface water management or those that can operate exclusively in dry conditions do not take into account the specific safety requirements necessary for mining operations that involve explosive gases. Additionally, the idea of a pump that can only be operated on weekends is irrelevant to the concept of permissibility in this context.