Which material is not approved as a flue lining for low-heat appliances?

Which material is not approved as a flue lining for low-heat appliances?

• A. Clay tile
• B. Masonry block
• C. Ceramic tile
• D. Stainless steel

Answer: (B)

The lining material for a chimney must be a listed, noncombustible interior that can safely withstand flue gases and heat. For low-heat appliances, approved options are ceramics such as clay tile, ceramic tile, and factory-built stainless steel liners. Masonry block isn’t approved because it’s porous and not rated as a proper liner; it can deteriorate with heat, absorb moisture, and fail to provide a smooth, continuous bore, increasing creosote buildup and fire risk. That’s why masonry block is not acceptable as a flue lining.

The lining material for a chimney must be a listed, noncombustible interior that can safely withstand flue gases and heat. For low-heat appliances, approved options are ceramics such as clay tile, ceramic tile, and factory-built stainless steel liners. Masonry block isn’t approved because it’s porous and not rated as a proper liner; it can deteriorate with heat, absorb moisture, and fail to provide a smooth, continuous bore, increasing creosote buildup and fire risk. That’s why masonry block is not acceptable as a flue lining.