18-28-507.6 Supports.

   Type I hoods shall be secured in place by noncombustible supports. All Type I and Type II hood supports shall be adequate for the applied load of the hood, the unsupported ductwork, the effluent loading, and the possible weight of personnel working in or on the hood.

18-28-507.7 Hood joints, seams and penetrations.

   Hood joints, seams and penetrations shall comply with Sections 18-28-507.7.1 and 18-28-507.7.2.

18-28-507.7.1 Type I hoods.

   External hood joints, seams and penetrations for Type I hoods shall be made with a continuous external liquid-tight weld or braze to the lowest outermost perimeter of the hood.

   Internal hood joints, seams, penetrations, filter support frames, and other appendages attached inside the hood shall not be required to be welded or brazed but shall be otherwise sealed to be grease tight.

   Exceptions:

      1.   Penetrations shall not be required to be welded or brazed where sealed by devices that are listed for the application.

      2.   Internal welding or brazing of seams, joints, and penetrations of the hood shall not be prohibited provided that the joint is formed smooth or ground so as to not trap grease, and is readily cleanable.

      3.   External hood joints and seams tested and listed in accordance with the requirements of UL 710 shall not be required to be welded or brazed.

18-28-507.7.2 Type II hoods.

   Joints, seams and penetrations for Type II hoods shall be constructed as set forth in Article 4, Duct Systems and shall be sealed on the interior of the hood and shall provide a smooth surface that is readily cleanable and water tight.

18-28-507.8 Cleaning and grease gutters.

   A hood shall be designed to provide for thorough cleaning of the entire hood. Grease gutters shall drain to an approved collection receptacle that is fabricated, designed and installed to allow access for cleaning.

18-28-507.9 Clearances for Type I hood.

   A Type I hood shall be installed with a clearance to combustibles of not less than 18 inches (457 mm).

   Exception: Clearance shall not be required from gypsum wallboard attached to noncombustible structures provided that a smooth, cleanable, nonabsorbent and noncombustible material is installed between the hood and the gypsum wallboard over an area extending not less than 18 inches (457 mm) in all directions from the hood.