For a gas appliance to use a masonry chimney, what type of lining is required?

A masonry chimney is designed to vent gases from combustion appliances safely, and the lining is crucial for its functionality and safety. Clay or metal linings are required for gas appliances using a masonry chimney because they are able to withstand high temperatures and corrosive exhaust gases.

Clay liners are typically used due to their durability and ability to resist deterioration over time while also providing good insulation. Metal liners, often made of stainless steel, are favored in situations that require a more flexible solution or where the chimney might experience condensation issues, as metal can cope with moisture and acidic gases better than unlined masonry.

Using improper materials would pose risks such as cracking, which could lead to combustion gases leaking into living spaces or the potential for chimney fires as a result of flammable creosote buildup. Thus, for both safety and efficiency, it is essential that the linings are specifically listed for the type of gas appliance being utilized.