The effective venting area shall not be less than 3-1/2 percent of the maximum shaft area at any floor, but in no event less than 72 square inches (0.05 m2). Of the total required vent area, at least one-third shall be clear opening to the exterior in the form of fixed louvers, ridge vents, or hooded or goosenecked openings. The remaining portion of the required vent area may be a window or skylight glazed with plain glass not more than 1/8-inch (3.2 mm) thick or with plastic glazing.
Exception: The clear opening to the exterior may be constructed as a skylight or trapdoor arranged to open automatically by fusible link or other mechanical device when subjected to a temperature of 160°F (71°C) or to a rapid rise in temperature at a rate of 15°F (-9.4°C) to 20°F (-6.7°C) per minute.
Where a closed shaft or smoke vent duct penetrates through the roof of the building, the vent shall be located as follows:
1. The vent shall be located at least 8 inches (203 mm) above a noncombustible roof assembly or at least 36 inches (914 mm) above a combustible roof assembly.
2. The vent shall be located at least 10 feet (3048 mm) from any window, door, exterior stairway, or interior lot line. The vent may be located no less than 5 feet (1524 mm) from any window or door provided that the vent is located at a point higher than the top of such window or door.
3. Where the vent is constructed as a window or louver, the sill of the window or louver shall be located at least 36 inches (above the roof assembly.