Section 809
SECTION 809. Vent Shafts. (a) Ventilation or vent shafts shall have a horizontal cross- sectional area of not less than 0.10 square meter for every meter of height of shaft but in no case shall the area be less than 1.00 square meter. No vent shaft shall have its least dimension less than 600 millimeters. (b) Skylights. Unless open to the outer at the top for its full area, vent shaft shall be covered by a skylight having a net free area or fixed louver openings equal to the maximum required shaft area. (c) Air ducts shall open to a street or court by a horizontal duct or intake at a point below the lowest window opening. Such duct or intake shall have a minimum unobstructed cross-sectional area of not less than 0.30 square meter with a minimum dimension of 300 millimeters. The openings to the duct or intake shall not be less than 300 millimeters above the bottom of the shaft and the street surface or level of court at the respective ends of the duct or intake.