Which type of material should be used for stoppings between airways that are not required for air passage?

Using incombustible or fire-resistant materials for stoppings between airways that are not required for air passage is essential for safety in underground mining environments. Stoppings serve to control airflow and prevent the spread of gases, smoke, or fires from one area to another. When fire-resistant materials are used, they help contain combustion within a specific area, significantly reducing the risk of fire propagation through the mine.

Choosing materials that are incombustible ensures that in the event of a fire, the stoppings will not ignite or contribute to the fire's severity. This not only protects the structural integrity of the stoppings themselves but also enhances the safety of miners by minimizing the potential for hazardous conditions to develop.

In contrast, flexible, lightweight, or chemically treated wood materials may not provide the same level of fire safety and can pose risks in terms of combustion or structural weaknesses in emergency situations. Thus, utilizing incombustible or fire-resistant materials is the most prudent choice for ensuring safe and effective stoppings in underground mining operations.