Section 27-521.12. Construction; general

(a) A mall may be constructed only
  in buildings in noncombustible construction groups 1-A, 1-B and 1-C.
    (b) The minimum horizontal clear dimension at  any  level  in  a  mall
  shall be twenty feet.
    (c)  Where  different  tenancies have openings to a mall the tenancies
  shall be separated in accordance with section 27-341 of article five  of
  subchapter five of this chapter.
    (d)  All  openings  between  a mall and other spaces shall be provided
  with a noncombustible draft curtain that shall extend downward a minimum
  of twenty-four inches below the lowest ceiling adjacent  to  such  draft
  curtain or shall meet the requirements of clause three of subparagraph d
  of  paragraph three of subdivision (h) of section 27-370 of article five
  of subchapter six of this chapter relating to show windows.