What is the effect of decreased mine resistance on fan performance?

The correct answer highlights that decreased mine resistance allows the fan to circulate a greater volume of air while maintaining the same level of ventilating pressure. When there is less resistance in the mine's ventilation system, it becomes easier for the fan to push air through. This means that the fan can move a larger quantity of air more efficiently without requiring additional pressure.

This principle is fundamental in mine ventilation systems, where the design aims to optimize airflow for safety and operational efficiency. By reducing obstacles like duct restrictions, bends, and blockages, the overall resistance in the ventilation system decreases, allowing the fan to perform more effectively. Therefore, having lower mine resistance is crucial for maximizing airflow, supplying fresh air to the working areas, and enhancing overall air quality in the mine.

In contrast, the other statements do not accurately describe the relationship between mine resistance and fan performance.