Grease or kitchen extract ductwork is usually made out of metal, commonly galvanised sheet metal in a rectangular or spiral-wound round structure, but can even be constructed from all-welded ‘black iron’ or stainless-steel. RAH models significantly reduce hearth chance by doing away with ductwork to outside and suppressing grease deposits https://kitchenextractsystems34455.estate-blog.com/28465620/kitchen-extract-systems-an-overview