A device installed in a fuel storage tank that is capable of sounding an alarm, during a filling operation, when the liquid level nears the top of the tank.
A high-level alarm is acceptable as an overfill prevention device in an underground storage tank according to federal rules, but is used primarily in aboveground tanks.
Fire codes require that alarm systems used in aboveground tanks be independent of gauging equipment used in the tanks. The systems must be designed to sound an alarm when the liquid in the tank reaches a prescribed level.
See also High-level valve.