How to clean smoke chamber and voids? I have 2 clay flues, one to the basment and one stops at the fireplace. There is a large void between the 2 flues and the brick walls of the chimney that seems to be fair full of creaote deposits from a coal/wood stove that was vented only as far as the damper plate. How am I to clean these voids as there is no way to access them from the top and they are irregularly shaped. I'm installing an insert with a full length liner. How concerned should I be?