18-28-506.3.12 Fire-resistive access opening.
   Where cleanout openings are located in ducts within a fireresistance-rated enclosure, access openings shall be provided in the enclosure at each cleanout point. Access openings shall be equipped with tight-fitting sliding or hinged doors that are equal in fire-resistive protection to that of the shaft or enclosure. An approved sign shall be placed on access opening panels with wording as follows:
   "ACCESS PANEL. DO NOT OBSTRUCT."