Which type of venting material has been discontinued for Category III appliances?

The type of venting material that has been discontinued for Category III appliances is high temp plastic vent (HTPV). Category III appliances operate with positive pressure venting and can produce high-temperature flue gases.

High temp plastic venting systems are not rated to handle the temperatures typically produced by these appliances, which can lead to concerns regarding structural integrity and safety. The use of materials that can withstand high temperatures and pressures, like stainless steel and galvanized steel, is essential to ensure both the efficiency of the appliance and the safety of the installation.

This change in guidelines is crucial because it helps prevent potential hazards such as venting failure or toxic gas leaks, which could arise if inappropriate materials are utilized for such demanding applications.