What is NOT a requirement for sealing the entrances of an underground mine?

The correct answer identifies easy access for personnel as not being a requirement for sealing the entrances of an underground mine. When sealing a mine, the primary concerns typically revolve around ensuring that the mine is effectively isolated from the surface environment to prevent any potential hazards, such as the escape of harmful gases or water influx.

Sealing is more about safety and environmental protection than facilitating regular access for personnel. The other aspects mentioned—like the capability of sealing without surface access, monitoring the atmosphere from a safe distance, and having an appropriate air-lock system—all serve crucial safety functions during the sealing process and help to maintain mine integrity after closure.

For instance, sealing without surface access ensures that no one inadvertently enters a dangerous area, while monitoring atmospheric conditions ensures that any hazardous situations can be managed without direct exposure to risk. The air-lock requirement relates to maintaining pressure differentials and safety standards during sealing operations.

The focus on mine safety and environmental protection is paramount, which is why easy access for personnel does not form part of the sealing requirements.