Use for venting listed natural gas or liquid propane Category I, draft hood apliances, or appliances that have been specifically tested and listed to use Type B Gas Vent. The appliances listed typically use Type B GasVent systems, but not always: Furnaces, Water Heaters, Boilers, Room Heaters, Decorative Gas Appliances, and Unit Heaters.
To calculate installed length, subtract 1 1/2" from each connection of vent. A 1" clearance (air space) to combustible materials must be maintained. To calculate OD add 5/8".