Type B vent is:

Type B vent is classified as a double wall venting system. This design features two concentric pipes: the inner pipe carries the flue gases, while the outer pipe serves to maintain proper temperatures and provide insulation. The double wall construction allows for a safer venting system by providing a barrier that helps to prevent heat transfer to surrounding materials, reducing the risk of fire hazards.

Type B vents are specifically engineered for gas appliances and help to ensure efficient venting of combustion gases. The double wall configuration not only aids in maintaining the correct temperature but also aids in reducing the likelihood of condensation that can occur in the venting system, which is crucial for the proper operation of gas-fired appliances.