Unlisted food service counter appliances shall not be set on combustible material
unless they have legs that provide not less than 4 inches (102
mm) of open space below the burners and the combustible surface is protected with insulating millboard not less than 1/4
of an inch (6.4 mm) thick covered with sheet metal not less
than 0.0122 of an inch (0.3099 mm) thick, or with equivalent
protection. [NFPA 54:10.13.4]