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When a vent is less than 10 feet high, the vent should be at least as large as the flue collar outlet.b) Vents for draft hoods or flue collars 12 inches in diameter or less should NOT be reduced more than one pipe size.
All open vent pipes that extend through. a roof shall be terminated at least [NUMBER] inches (mm) above the roof, except that where a roof is to be used for any. purpose other than weather protection, the vent extensions. shall be run at least 7 feet (2134 mm) above the roof.