Oil Tanks shall be equipped with a ________________ device.

The correct answer is gauging device, as it is crucial for monitoring the level of fuel oil in storage tanks. This device helps ensure that the operator can regularly assess the amount of oil available, which is important for safe operations and to prevent overfilling. Additionally, a gauging device can also play a role in inventory management and leak detection, enhancing the safety of the system by alerting users to potential issues before they escalate.

While safety valves, pumps, and vent pipes serve important functions within oil tank systems—such as preventing pressure buildup, facilitating the transfer of oil, and allowing for vapor expansion—they do not specifically address the need for level monitoring, which is the primary function of a gauging device.