§ 266. Exterior enclosed fireproof stairway. "Exterior enclosed\nfireproof stairway" means a stairway conforming to the following\nrequirements:\n 1. It shall be completely enclosed from top to bottom by walls of\nfireproof material not less than eight inches thick extending from the\nsidewalk, court or yard level to the roof, and above the roof so as to\nform a bulkhead.\n 2. It shall in all other respects except as herein provided conform to\nthe requirements of section two hundred and seventy in regard to the\nconstruction of stairways and their enclosures, except that stairways\nand landings in an exterior fireproof enclosed stairway not exceeding\none hundred feet in height may be constructed of other than\nincombustible material to be approved by the board.\n 3. There shall be n
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§ 266. Exterior enclosed fireproof stairway. "Exterior enclosed\nfireproof stairway" means a stairway conforming to the following\nrequirements:\n 1. It shall be completely enclosed from top to bottom by walls of\nfireproof material not less than eight inches thick extending from the\nsidewalk, court or yard level to the roof, and above the roof so as to\nform a bulkhead.\n 2. It shall in all other respects except as herein provided conform to\nthe requirements of section two hundred and seventy in regard to the\nconstruction of stairways and their enclosures, except that stairways\nand landings in an exterior fireproof enclosed stairway not exceeding\none hundred feet in height may be constructed of other than\nincombustible material to be approved by the board.\n 3. There shall be no opening in any wall separating it from the\nbuilding.\n 4. Access shall be provided to the stairway from every floor of the\nbuilding by means of an outside balcony or vestibule of steel, iron or\nmasonry. Every such balcony or vestibule shall have an unobstructed\nwidth of at least forty-four inches and shall be provided with a\nfireproof floor and a railing of incombustible material not less than\nthree feet high. Access to such balconies from the building and to the\nstairway from the balconies shall be by means of firedoors. The level of\nthe balcony floor shall be not more than seven inches below the level of\nthe door sill of the building. The doors shall swing outward onto the\nbalcony and inward from the balcony to the stairway, and shall be\nprovided with locks or latches with visible fastenings requiring no key\nto open them in leaving the building. The balconies shall be open on at\nleast one side, upon an open space not less than one hundred square feet\nin area.\n 5. The landings shall be of such width that the doors in opening into\nthe stairway shall not reduce the free passageway of the landings to a\nwidth less than the width of the stairs.\n 6. Such stairway shall be provided with a proper lighting system\nfurnishing adequate light and shall be so arranged as to ensure its\nreliable operation, when through accident or other cause the regular\nfactory lighting is extinguished.\n