N.Y. Multiple Dwelling Law § 178: Lighting and ventilation of stairs

§ 178. Lighting and ventilation of stairs. Where the stair and public

halls are not provided on each story with windows opening to a street,

yard or court, a skylight equipped with ridge ventilators having an

opening of forty square inches or more shall be provided in the roof

over the stair, except as otherwise provided in paragraph g of

subdivision three of section one hundred seventy-one. The glazed roof of

such skylight shall not be less in area than nine square feet nor less

than two feet in its least dimension, provided the ventilating and glass

areas in such skylight are not less than herein required; except that in

dwellings converted before April eighteenth, nineteen hundred

twenty-nine, where a skylight smaller than such prescribed dimensions

was in existence on such date, no structural change shall be required,

but a ventilating skylight fitting the existing skylight opening in the

roof beams shall be deemed sufficient.