Section 268. Exterior screened stairway

"Exterior screened stairway" means
  a stairway conforming to the following requirements:
    1. It shall be built of incombustible material.
    2. The risers  of  the  stairs  shall  not  be  more  than  seven  and
  three-quarters  inches in height and the treads not less than ten inches
  wide.
    3. On each floor there shall be a balcony connecting with the stairs.
    4. Access to the balconies shall be by means of fire  doors  extending
  to  the floor level and which shall slide freely or open outwardly so as
  not to obstruct the passageway.
    5. All windows or other openings upon the course of such stairs  shall
  be fireproof.
    6.  The level of the balcony floor shall not be more than seven inches
  below the level of the door sill.
    7. The stairs shall continue from the roof to  the  ground  level  and
  shall  lead  (a)  directly  to  a street, or (b) to a fireproof enclosed
  passageway independent of other exit from the building and leading to  a
  street  or  road,  or  (c)  to  an open area having communication with a
  street or road.
    8. The balconies and stairs shall be guarded on the sides by a  screen
  of incombustible material.