Where must all main fans in a mine be installed?

The correct answer is that all main fans in a mine must be installed on the surface. This is a critical safety and operational requirement in mining operations. Installing fans on the surface allows for better airflow management and easier maintenance. It ensures that the fans can circulate fresh air into the mine efficiently while also drawing out stale or harmful air, including gases that may accumulate underground.

Additionally, surface installation minimizes the risk of mechanical failure in an environment where conditions can be harsh and challenging, thus ensuring the reliability of the ventilation system. Installing fans in a more controlled environment, like the surface, also helps prevent issues related to debris or moisture that can occur in underground settings.

In contrast, installing fans in underground tunnels or near exit shafts can lead to insufficient air circulation and potential exposure to dust and contaminants that could impair fan performance. Similarly, placing fans within the main working area could pose safety risks to miners and impede their work processes. Effective ventilation is crucial for ensuring a safe mining operation, and surface installation of main fans is a standard best practice in the industry.