N.Y.C. Admin. Code § 27-747: § 27-747 Alcoves.

An alcove or room opening off another room or space shall be considered as a separate room in determining its requirements for ventilation. However, for dwellings classified in occupancy group J-3, where the opening between the alcove and the room or space is at least eighty percent of the area of the common wall and the floor area of the alcove does not exceed twice the area of the opening, the alcove and the room opening into the alcove may be considered as a single space.