For purposes of tank entry, cleaning, or repair, a tank that meets all three of the requirements for a confined space and also has one or more of the following four characteristics: (1) contains or has the potential to contain a hazardous substance, (2) contains a material with the potential to engulf an entrant, (3) has an internal configuration such that an entrant could become trapped or asphyxiated by inwardly converging walls or floor that slope downwards, tapering to small cross sections, (4) contains any other recognized serious safety or health hazard.