Which vents are suitable only for listed, draft hood-equipped, gas-fired appliances?

Type B vents are designed specifically for use with listed, draft hood-equipped, gas-fired appliances. These vents are double-wall structures that provide a safe path for the exhaust gases produced by the appliance while maintaining sufficient heat to prevent condensation. The design of Type B vents ensures that they can handle the lower flue gas temperatures typically produced by gas appliances operating under various conditions.

Using Type B vents is crucial because they comply with safety standards that account for the characteristics of gas-fired appliances, such as the presence of draft hoods. A draft hood is a critical component that helps ensure proper venting and adequate combustion air supply, which is vital for the safe and efficient operation of the appliance. In contrast, other types of vents, such as Type A, Type C, and Type D, serve different purposes and are not suitable for appliances equipped with draft hoods, as they may not meet the necessary safety requirements or handle exhaust correctly.