The installation, alteration, repair and additions to attic units shall be subject to the following requirements: attic furnaces shall be installed with clearance as provided by the Chief of the Fire Department and the Building Inspector. The furnace shall be set in a sheet metal pan with a minimum of two inches depth to extend six inches from the widest point on all four sides and such pan shall have an asbestos or other fireproof material three-sixteenths inch thickness between the pan and combustible material. Adequate permanent accessibility shall be provided such as a disappearing stairway or stationary ladder. (1970 Code Sec. 14-4)