Why are overcasts generally preferred to undercasts?

Overcasts are generally preferred to undercasts primarily because undercasts can be negatively affected by environmental factors, such as filling with debris or water. This is a significant concern in underground mining, where the buildup of water or material can obstruct airflow and create hazardous conditions. An overcast, on the other hand, allows air to flow freely above the potential blockages, thereby maintaining better air quality and circulation in the mine.

In addition, while it is true that overcasts can be easier to manage in terms of ensuring airflow, the primary reason for their preference is linked to the structural integrity and functionality. Maintaining a clear pathway for air through an overcast structure is key to a safe working environment. Ensuring continuous, unobstructed airflow helps in controlling dust and gases, which are crucial for the safety and health of miners.