1.1 Covers the design and construction of Type B (round or oval) and Type Bw
Gas Vents. Type B Gas Vents are intended for the venting of flue gases having
temperatures not exceeding 245 degrees C, from gas-fired appliances certified
with draft hoods or diverters. Type BW Gas Vents are intended for the venting
of flue gases from gas-fired wall furnaces and the maximum input to a Type Bw
Gas Vent is determined by the maximum input of the vented wall furnace to which
the type BW Vent is intended to be connected. 1.2 Type B Gas Vents are also intended for use with gas-fired appliances,
without draft hoods or diverters, which meet all of the following requirements: A The appliance is certified for use with a Type B Gas Vent; B Flue gas temperatures normally exceed 135 degrees C but do not exceed 245
degrees C; C The vent normally operates below atmospheric pressure; and D Condensation of flue gas products is not normally expected within the vent. 1.3 Gas vents are intended for installation in accordance with the National
Building Code of Canada and the Installation Code for Gas Burning Equipment,
CAN/CGA-B149.1 and CAN/CGA-B149.2, or the acts or regulations of the authority
having jurisdiction. They are intended primarily for installation inside
buildings to provide an essentially vertical conduit or passageway for
conveying flue gases to the outer air from the above-described class of
appliances. They may be used on the exterior of buildings when enclosed and
specifically certified for such an application.