All materials and appliances used in the installations which are covered by this chapter shall be approved. Unless otherwise specified in this chapter, materials and appliances listed in the copyrighted lists of inspected appliances and supplements published by the Underwriters' Laboratories shall be made in conformity with approved methods of construction for safety to life and property, and when so made, shall be considered to be approved. New materials manufactured from time to time and approved by the National Board of Fire Underwriters may be made a part of this chapter when and if approved by the inspector. Such approval must be in writing and attached to all copies of this chapter on file in City Hall. (Prior code § 16-1-9)