§ 189. Stair and public hall construction. Except as provided in paragraph g of subdivision three of section one hundred seventy-one, stairs and public halls shall conform to the following provisions:

1. In a dwelling more than a basement and three other stories in height or occupied by four families or more, the soffit and stringers of every stair between the lowest entrance story and the next higher story and the walls and ceilings of every lowest entrance hall shall be fire-retarded and in such dwellings converted on and after July first, nineteen hundred fifty-eight, all doors opening to such entrance hall and stairs, and the door assemblies, shall be fireproof with the doors self-closing. In lieu of the requirements of this subdivision, a sprinkler system may be installed in accordance with the provisions of section one hundred eighty-seven.

2. Every door opening from any stair, entrance hall or other public hall to any other part of the dwelling shall be self-closing. Every glazed transom over any such door shall be glazed with wire glass. Every transom shall be stationary. On and after July first, nineteen hundred fifty-seven, every glazed panel or other glazed opening in any such door shall be glazed with wire glass.

3. Every stair, except a basement or cellar stair, shall be two feet six inches or more in clear width. Any wooden stair may be replaced by an iron stair of like dimensions. Every entrance hall shall be two feet eight inches or more in clear width.

4. If the number of rooms in a class B dwelling is increased and there are sixteen sleeping rooms or more above a basement or, if there be no basement, above the main entrance story, all partitions and ceilings enclosing public halls and stairs shall be fire-retarded throughout. All doors opening to such public halls and stairs, and their assemblies, shall be fireproof with the doors self-closing. Stairs shall be fireproof and shall extend from the main entrance story through a bulkhead to the roof.

5. On and after July first, nineteen hundred fifty-seven, every interior sash, or opening other than a door, in the walls or partitions of any stair, entrance hall or other public hall, and every window therein not opening to the outer air, shall be removed and the openings closed up with material similar to the adjacent walls.