Domestic open-top broiler units shall be provided with a metal ventilating hood not less than 0.0122 inch (0.3 mm) thick with a clearance of not less than 1/4 inch (6 mm) between the hood and the underside of combustible material or metal cabinets. A clearance of at least 24 inches (610 mm) shall be maintained between the cooking top and the combustible material or metal cabinet, and the hood shall be at least as wide as the open-top broiler unit and centered over the unit. Listed domestic open-top broiler units incorporating an integral exhaust system and listed for use without a ventilating hood need not be provided with a ventilating hood if installed in accordance with 18-28-917.7.1.2(1)