Section 27-805. General requirements

Clearances   from   combustible
  construction in walls, partitions and ceilings adjacent to combustion or
  heating equipment shall not be less than  that  tabulated  in  reference
  standard RS 14-15, provided the following conditions are met:
    (a)  All  clearances  shall  comply with the requirements specified in
  section 27-792 of article one of this subchapter.
    (b)  Heating  and  combustion  equipment  which  has  been  tested  in
  accordance  with  the  applicable standards listed in reference standard
  RS-14, shall be installed with the clearances determined by such tests.
    (c) Equipment which has been approved, as provided in  section  27-135
  of  article  eight of subchapter one of this chapter, shall be installed
  in accordance with the conditions of such approval.