N.Y.C. Admin. Code § 27-521.12: § 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.