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1.1 The requirements of this Standard cover the design and construction of Type B (round or oval) and Type BW Gas Vents.
1.2 Type B Gas Vents are intended for the venting of flue gases having temperatures not exceeding 245 °C, from gas fired appliances certified with draft hoods or diverters. 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 °C but do not exceed 245 °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 Type BW Gas Vents are intended for the venting of flue gases from recessed gas fired wall furnaces. 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.
1.4 Gas vents are intended for installation in accordance with the National Building Code of Canada and the Natural Gas and Propane Installation Code, CSA B149.1, 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 tested for such an application.