What condition allows a maximum 660-gallon storage tank to be installed on a higher floor?

The condition that allows a maximum 660-gallon storage tank to be installed on a higher floor is that the higher floor has a liquidtight sill. This requirement is in place to prevent any potential leakage of fuel from the tank. If there were to be a leak, the liquidtight sill serves as a protective barrier, effectively containing any spillage and preventing it from spreading to other areas, which is crucial for safety and environmental protection. The use of a liquidtight sill is a fundamental safety measure intended to mitigate the risks associated with tank installations in elevated locations, where spills could create more significant hazards.