This unit must be installed with a liner adapter and a length of flexible stainless liner routed up the chimney flue. Without the liner in place, the insert will not draw properly. A complete kit that can be used with this model is the DuraFlex 6 Inch Diameter x 15 Foot Long Kit of 304-Alloy Light Chimney Liner
. Longer kits for taller chimneys are also available.