Check the register plate

The register plate seals the chimney opening above the stove, directing all the flue gases into the liner and stopping cold air, debris, and birds from coming down around the outside of the pipe. If yours has a gap around the liner, or the plate itself has rusted through, you'll feel draughts, smell must, and potentially lose smoke up the chimney cavity rather than into the liner.

Check the plate for rust, holes, and the condition of the seal around the liner. Rope seal is often used here and needs the same periodic replacement as the door rope. If the plate is badly corroded, it needs replacing. This is usually a job that benefits from having a sweep look at the same time, as access involves some dismantling.

A properly sealed register plate also stops heat loss when the stove isn't lit. Cold air pouring down around the liner and into the room is one of the most common causes of a cold fireplace area even when the stove is working well.