NY Mult Dwell L § 150 (2021)
2021 New York Laws MDW - Multiple Dwelling Article 5 - Non-Fireproof Multiple Dwellings Title 1 - Fire Protection 150 - Cellar and Basement Stairs.

§  150. Cellar and basement stairs. 1. Except as otherwise provided in   this section, there shall be no inside stair communicating  between  the   lowest  cellar or the lowest story, if there be no cellar, and the floor   next above, but any stair communicating between  such  floors  shall  be   located  outside  the  dwelling  and if enclosed shall be fireproof in a   fireproof enclosure with fireproof doors and door assemblies,  with  the   doors self-closing, at all openings.2. This provision, however, shall not apply to any stair not extending   through  more  than  one  story and leading from an entrance hall to the   upper stories where the walls enclosing  such  hall  are  fireproof  and   unpierced  except  for openings to stairs, elevators, apartments, public   reception rooms, professional offices and the outer  air.  In  no  event   shall  there  be  any  other opening from such an entrance hall, and all   apartments and such professional  offices  opening  therefrom  shall  be   entirely  separated  from  any  space  within such dwelling used for any   other purposes by fireproof walls which shall be  unpierced  except  for   means  of  egress  into  the  entrance  hall.  The  provisions  of  this   subdivision shall  not  apply  to  openings  which  are  protected  with   fireproof   vestibules.   Any   such  vestibule  shall  have  a  minimum   superficial floor area of fifty square feet and its maximum  area  shall   not   exceed  seventy-five  square  feet.  It  shall  be  enclosed  with   incombustible partitions having a fire-resistive rating of three  hours.   The  floor  and ceiling of such vestibule shall also be of incombustible   material having a fire-resistive rating of at least three  hours.  There   shall  be  two  doors  to  provide access from the entrance hall and any   other space not used for  openings  to  stairs,  elevators,  apartments,   public  reception  rooms  and the outer air. Each such door shall have a   fire-resistive rating of one and one-half hours and  shall  be  provided   with a device to prevent the opening of one door until the other door is   entirely  closed. One of these doors shall swing into the vestibule from   the entrance hall and the other shall  swing  from  the  vestibule  into   space  which  it  serves.    Such  vestibule shall also be equipped with   sprinklers and  with  an  independent  exhaust  duct  having  a  minimum   cross-sectional  area  of  one hundred forty-four square inches for each   one thousand cubic feet, or fraction thereof, of air content,  and  such   exhaust duct shall not be connected with any other ventilating system.3.  In dwellings three stories or less in height which are occupied by   two families or less on every story, any stair leading to the cellar may   be located inside the dwelling provided it  is  entirely  enclosed  with   fireproof walls and with fireproof doors and door assemblies at both the   cellar level and the story above, with the doors self-closing.4. The provisions of subdivision one shall not prohibit or apply to an   inside  stair extending from a space used for commercial purposes in the   cellar or lowest story to a store on the story next above, provided such   stair is of incombustible materials,  has  closed  risers,  is  enclosed   between  the  two  lowest  floors  with  walls  having a three-hour fire   resistive rating and has fireproof doors and door assemblies at top  and   bottom,  with the doors self-closing, and provided such commercial space   in the cellar or lowest story is  completely  enclosed  with  partitions   having  a  fire-resistive  rating  of at least two hours and there is no   opening between the store on the story next above and any entrance  hall   or other public hall or public portion of the dwelling.