18-28-504.9.1 Material and size.
   Exhaust ducts shall have a smooth interior finish and shall be constructed of metal not less than 0.016 inch (0.4 mm) in thickness. The exhaust duct size shall be 4 inches (102 mm) nominal in diameter.
(Amend Coun. J. 9-14-21, p. 35949, Art. V, § 11)