Simpson DuraVent's Type B Gas Vent system. Use with natural gas or liquid propane category I and drafthood equipped appliances, and appliances tested and listed to use Type B Gas Vent. Applications include: natural gas fireplaces, gas-fired furnaces, boilers, water heaters, and wall or space heating applications. Type B Gas Vent has been engineered to heat up rapidly. It remains hot during the operation of the appliance with minimal condensation on the appliance and vent system. Simpson DuraVent Type B Gas Vent is designed to meet the rugged demands of the job site. The inner wall is recessed to eliminate damage in handling.ADA Compliant: No Collection: DuraConnect I Fuel Type: Natural Gas, Liquid Propane Height: 24 Material: Aluminum Pipe Class: Type B Pipe Inside Diameter: 4 Pipe Shape: Round Style: Contemporary Modern UL Listed: Yes Vent Construction: Single Wall