In any existing building classified in occupancy group J-1, either seventy-five feet or more in height or containing thirty or more sleeping rooms:
(a) Where a corridor or space above a ceiling in a corridor is being used on or after February first, nineteen hundred eighty-four to furnish direct ventilation to a sleeping room or suite, such use shall, unless continued use is permitted by the commissioner, be discontinued by closing all openings between the corridor and sleeping room with construction having a fire-resistance rating equal to the construction in which the opening occurs. When continued use of corridor spaces as a plenum is permitted, smoke detecting devices shall be installed in accordance with the requirements of section 27-981 of article six of subchapter seventeen of this chapter and activation of any two detectors on a floor shall cause closure of all openings to that floor and shut-off of ventilation service to the floor.
(b) All corridors and other public areas not provided with natural ventilation meeting the requirements of section 27-761 of article eight of subchapter twelve of this chapter shall be provided with manual smoke purging by means of existing ventilation systems.
(c) The requirements of this section shall be complied with on or before April first, nineteen hundred eighty-seven.