§ 270. Construction of buildings erected after October first, nineteen
hundred and thirteen. No factory shall be conducted in a building
erected after October first, nineteen hundred and thirteen, unless such
building shall conform to the following requirements:

1. Fireproof construction. All buildings more than four stories in
height shall be fireproof.

2. Roofs and walls. Roofs shall be covered either with incombustible
material, or tar and slag, or plastic cement or such other materials as
the board may approve, supported and laid according to its
specifications. Cornices shall be constructed of incombustible material.
All exterior walls within twenty-five feet of a non-fireproof building
shall be built of brick, stone, concrete, cinder or concrete block or
tile, terra cotta or other fireproof material acceptable to the state
department of labor.

3. Required exits. a. On each floor used as a factory there shall be
not less than two exits remote from each other, except that a single
exit may be accepted by the commissioner from a floor or other area, of
one thousand square feet or less, so long as no person is regularly
employed on such floor or other area. One such exit on each floor used
as a factory shall be a grade exit, an interior or exterior enclosed
fireproof stairway or ramp. The other shall be either such a grade exit,
stairway, ramp, or a horizontal exit, except that unenclosed exterior
stairways or ramps within the property line, extending up or down to
grade may be substituted for enclosed stairways from a floor immediately
above or below the ground or first floor. Elevated runways and working
platforms on which there is no regular or permanent occupancy shall not
be construed as floors.

b. No point in any floor above or below the ground or first floor
shall be more than one hundred feet distant from the entrance to one
such exit at that floor and in a sprinklered building more than one
hundred and fifty feet distant from such exit. No point in any ground,
or first floor shall be more than two hundred feet distant from an exit
from that floor and in a sprinklered building more than two hundred and
fifty feet distant from such exit; provided that no point in any ground,
or first floor of a building erected after July first, nineteen hundred
forty-eight, in which a factory is conducted, shall be more than one
hundred fifty feet distant from an exit from that floor and in a
sprinklered building more than two hundred feet distant from such exit.

c. In every building over one hundred feet in height there shall be at
least one exterior fireproof enclosed stairway which shall be accessible
from any point in the building.

4. Stairways and ramps. a. All required interior stairways and ramps
shall be constructed of incombustible material. Two hour fire test
enclosures shall be provided in buildings over two stories in height,
and in all subgrade stories. One hour fire test enclosures shall be
provided for all other stairs and ramps in buildings two stories or less
in height. All stairways and ramps shall have an unobstructed width of
at least forty-four inches throughout their length except that hand
rails may project not more than three and one-half inches into such
width. There shall be not more than twelve feet six inches in height
between successive landings. The treads shall be not less than ten
inches wide and the risers shall be closed and not more than seven and
three-fourths inches. No stairway with "winders" shall be permitted as a
required exit. The treads shall be constructed and maintained so as to
prevent persons from slipping thereon. Ramps used in place of required
exit stairways shall have a slope not exceeding one foot in eight feet
and shall comply with the requirements for stairways as to material,
width, enclosure, ventilation, landings and shall have non-slip
surfaces.

b. Every such required interior stairway shall be enclosed and
ventilated in a manner conforming to rules adopted by the board, except
that unenclosed stairways, no part of whose floor opening is more than
twenty feet from an open side of the mezzanine and which lead to the
floor immediately below, may be accepted from an unenclosed mezzanine
not exceeding twenty-five hundred feet in area, unless otherwise
specified by the board in its rules.

c. Exterior windows within twenty-five feet of a non-fireproof
structure shall be fire windows. Skylights, unless provided with wired
glass, shall have thereunder a shield of wire mesh in substantial frame
work.

d. Whenever safe egress may be had from the roof of a building
exceeding two stories in height to an adjacent structure all stairways
serving as required exits shall extend to the roof, provided that in
buildings over five stories in height at least one of the stairways
serving as required exits shall extend to the roof. All stairways
serving as required exits shall lead (a) continuously to the street, or
(b) to a fireproof passageway independent of other exits from the
building opening on a road or street, or (c) to an open area affording
unobstructed passage to a road or street, except that unobstructed
access to exits on the floor immediately below may be accepted for
stairways from a mezzanine floor unless otherwise specified by the board
in its rules. Provision shall be made for the adequate lighting of all
stairways, ramps and passageways by artificial light. Where more than
two stairways are provided in a building, not more than two may lead
through a common fireproof passage to a street. Required stairways
terminating at a floor below roof shall be connected at floor at which
such stairs terminate through a fireproof passage to at least one other
required stairway.

5. Doors and doorways. All doors at required exits or that lead to
required exits shall open outwardly. The width of the fireproof
passageways and exit doorways including stops, leading to the street at
the grade level shall be not less than the aggregate required width of
all stairways and ramps leading to them. The aggregate capacity of all
other required exit doorways shall be calculated on the basis of
twenty-two inches for each fifty persons or fraction thereof to be
served by such doorways, but no such doorway shall be less than
thirty-six inches in width.

The provisions of this section shall not apply to a building, in a
city having a population of more than one million, used exclusively by
one employer and in which not more than one-tenth of all the persons
employed therein are engaged in work for a factory and which, except for
such factory work, would be classified as a mercantile establishment.