What must be installed where an outside tank supply line enters a building?

In this context, a thermally operated shutoff valve is required where an outside tank supply line enters a building to enhance safety by preventing fuel leaks in the event of a fire or excessive heat. This type of valve is designed to automatically close in response to elevated temperatures, thereby restricting the flow of combustible fluids when it is most critical to do so.

This safety feature minimizes the risk of fire spread from outside to inside the building by ensuring that any potential fuel leaks are contained. The installation of a thermally operated shutoff valve effectively addresses fire safety protocols outlined in the Maine Fuel Code and ensures compliance with safety regulations regarding fuel delivery systems.

The other options do not provide the same level of safety specific to this scenario. While a manual shutoff valve is useful for maintenance and operational control, it does not react automatically to dangerous conditions. A pressure relief valve is used to relieve excess pressure in a system, but it does not address the issue of external fire hazards. Similarly, a flow control valve regulates flow but does not offer the critical safety feature of automatic closure in the event of a fire. Thus, the thermally operated shutoff valve is the most appropriate choice for this specific installation requirement.