What type of material is commonly used for chimney liners?

Chimney liners are primarily made from clay, which is a traditional and widely used material due to its resistance to high temperatures and ability to withstand the corrosive effects of combustion gases. Clay liners can also effectively prevent creosote buildup, which is crucial for maintaining chimney safety and efficiency. Their thermal and structural properties help ensure that the chimney functions properly while minimizing the risk of fire or structural damage.

Other materials, such as metal or concrete, are also used for liners but are not present in this particular set of choices. Wood, plastic, and glass do not possess the necessary heat resistance or structural integrity to function effectively as chimney liners. Using these materials in a chimney system could lead to significant safety hazards, including fire risks and structural failures. Thus, clay stands out as the most appropriate choice for chimney liners when considering safety, durability, and effectiveness.