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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.
Type B Vents are factory built double wall vent pipes that are only used to for venting gas. They are always made with a galvanized exterior and an aluminum interior. The air space between walls is fairly small. This vent can be used as a vent or connector, and is quite inexpensive. Type L vents can be either a vent or a connector, and is made to vent oil. Class A chimneys are still preferred in the market over L vents, and as such L vents availability is limited. Sometimes it is listed for âbio-mass ventingâ, or venting the products of combusting pellets, corn, cherry pits, etc.