Why are vent alarms required for fuel oil tanks?

Vent alarms are required for fuel oil tanks primarily to provide an indicator of overflow. This is crucial for safety and environmental protection, as an overflow can lead to fuel spillage, which poses hazards such as fire risk and environmental contamination. By installing vent alarms, operators are alerted when the tank is close to full capacity, enabling timely action to prevent spills and ensuring that operations remain compliant with regulatory safety standards.

The other options do not directly relate to the primary function of vent alarms. Regulating temperature is more about maintaining the operational conditions of the fuel rather than monitoring its volume. Enhancing combustion efficiency pertains to how effectively the fuel burns, not to tank management or overflow monitoring. Lastly, while monitoring fuel density could be important for certain operational parameters, it is not the primary role of vent alarms in the context of preventing spillage and ensuring safe fuel management practices.