Section 190. Cellar stairs

1.  Except  as  provided  in  paragraph g of
  subdivision three of section one  hundred  seventy-one,  and  except  as
  otherwise provided in subdivision two hereof, every stair leading from a
  cellar  to  the  floor  above  shall  be  constructed  of  incombustible
  materials, shall have closed risers, shall be completely  enclosed  with
  partitions  of  incombustible  materials  and  shall  be equipped at the
  bottom with a fireproof door and assembly with the door self-closing.
    2. Every existing stair leading from a cellar to the floor above in  a
  converted  dwelling  accepted or approved by the department on or before
  July first, nineteen hundred sixty shall be deemed  in  compliance  with
  this section.