Type B vents are vents suitable only for listed, draft-hood equipped, gas-fired appliances, including most domestic heating and hot water systems.

What is B-vent duct?

Sometimes referred to as Natural Vent – B-Vent appliances use pipe (b-vent) that must be installed through the home and terminate above the roof. They also use room air for combustion, but the amount of air they use is minimal. Pros: Combustion fumes are vented outside.

Is B-vent a Category 3?

B-vent is ONLY allowed on Category 1 appliances unless the appliance manufacturer has specifically certified a particular B-vent system to be used alternatively.