Which type of vents are gas appliances listed and labeled for venting?

Gas appliances are typically listed and labeled for venting with Type B vents. Type B vents are specifically designed for the venting of gas-fueled appliances, and they are constructed to handle the flue gases produced by these appliances safely and efficiently.

These vents are equipped with a double-wall construction that allows for proper insulation and helps to maintain the necessary temperature to ensure that the gases rise properly and reduce the risk of condensation. This is crucial because improper venting can lead to increased risks of carbon monoxide buildup and potential hazardous situations.

Type A and Type L vents are used for different purposes. Type A vents are generally used for appliances that are not gas-fired, while Type L vents are specific to venting Category II, III, and IV appliances that can operate at lower temperatures and require higher clearances for safety. Therefore, Type B vents are the only option suited for the venting needs of most gas appliances, emphasizing their critical role in HVAC systems.