If ventilation doors are mechanically operated, what feature should they have?

Ventilation doors that are mechanically operated should have audible or visual warning devices as a feature to ensure safety in a mining environment. This feature serves a critical purpose by alerting personnel to potential hazards associated with the operation of the doors. For example, when doors are being opened or closed, having an audible or visual warning can help prevent accidents by ensuring that workers in the vicinity are aware of the movement, thereby reducing the risk of injury.

In mining operations, effective communication about door status not only enhances worker safety but also helps maintain proper airflow, which is vital for controlling the environment and reducing the risk of harmful gas accumulation. This focus on safety aligns with regulatory requirements and best practices in mine management.

Other options may provide various benefits; for instance, remote control capability and manual overrides can add convenience and flexibility in operations, while automated timers can help manage door operation schedules. However, the prioritization of audible or visual warning systems is essential for immediate safety awareness, making it the correct answer in this context.