No factory shall be conducted in a building erected before October first, nineteen hundred thirteen, and not occupied or used as a factory building on July first, nineteen hundred forty-eight, unless such building shall conform to the requirements of section two hundred seventy. No factory shall be conducted in a building erected before October first, nineteen hundred thirteen and occupied or used as a factory building on July first, nineteen hundred forty-eight, unless such building shall conform to the following requirements:
1. Required exits. a. On each floor used as a factory there shall be at least 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 shall be either a grade exit, an interior stairway enclosed as hereinafter provided or ramp similarly enclosed, or an exterior fireproof enclosed stairway. The other shall be: either such a grade exit, stairway or ramp; or a horizontal exit; or an exterior screened stairway; or outside fire-escapes on a building six stories or less in height, except such fire-escapes shall not be accepted as a required exit in such buildings or particular classes thereof where the board finds that they will not in its opinion furnish adequate and safe means of escape for occupants in case of fire. Unenclosed exterior stairways or ramps extending up to grade may be substituted for enclosed stairways from a floor area below the ground floor.b. No point on any floor above or below the ground floor shall be more than one hundred feet distant from the entrance to one such exit at that floor nor more than one hundred and fifty feet distant from such exit if the building has an automatic sprinkler system conforming to section two hundred and eighty and the rules of the board. No point in any ground floor area 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.c. If safe egress may be had from the roof to an adjacent structure every stairway serving as a required exit in a building exceeding two stories in height shall be extended to the roof. All such stairways shall extend to the first story and lead to the street or to an unobstructed passageway leading to a street or road or to an open area affording safe passage to a street or road.2. Stairway enclosures. All interior stairways serving as required exits and the landings, platforms and passageways connected therewith shall be enclosed on all sides by partitions of fire-resisting material extending continuously from the basement to the roof. Where the stairway continues to the top floor such partitions shall extend to three feet above the roof or to the roof if it is fireproof. All such partitions and doors provided for openings therein shall be constructed in accordance with rules adopted by the board.3. Doors. Where five or more persons are employed on any floor of a factory building all doors on such floor leading to or opening on any exit shall open outwardly or be double swinging doors. All exit doors in the first story, including the doors of the vestibule, shall open outwardly.