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 Vents covered by this Standard are intended for installation in accordance with applicable Codes,
such as:
a) The National Building Code of Canada; and
b) The Natural Gas and Propane Installation Code, CSA B149 Series.
1.5 The vents 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.