New York Consolidated Laws, Labor Law - LAB § 267. Horizontal exit

1. “Horizontal exit” means the connection by one or more openings, protected by firedoors, through a fire wall in any building, or through a wall or walls between two buildings, which doors shall continuously be unlocked and the opening unobstructed whenever any person is employed on either side of the opening.

2. Exterior balconies and bridges not less than forty-four inches in width connecting two buildings and not having a gradient of more than one foot fall in six, may also be counted as horizontal exits when the doors opening out upon said balconies or bridges are fireproof doors and are level with the floors of the building, and when all doors of both buildings opening on such balconies or bridges are continuously kept unlocked and unobstructed whenever any person is employed on either side of the exit, and when such balconies or bridges are built of incombustible material and are capable of sustaining a live load of not less than ninety pounds per square foot with a factor of safety of four;  and when such balconies or bridges are enclosed on all sides to a height of not less than six feet and on top and bottom by fireproof material, unless all windows or openings within thirty feet of such balconies in the connected buildings shall be encased in metal frames and sash and shall have wired glass where glass is used.

3. In any case there shall be on each side of the wall or partition containing the horizontal exit and independent of said horizontal exit, at least one stairway conforming to the requirements for a required exit.