Stair and elevator shaft vents and other outdoor air intakes and exhaust openings integral to the building envelope shall be equipped with not less than a Class I motorized, leakage-rated damper with a maximum leakage rate of 4 cfm per square foot (6.8 L/s • m 2 ) at 1.0 inch water gauge (w.g.) (1250 Pa) when tested in accordance with AMCA 500D.
Exception: Gravity (nonmotorized) dampers are permitted to be used in buildings less than three stories in height above grade.
Exception: Gravity (nonmotorized) dampers are permitted to be used in buildings less than three stories in height above grade.