Question: After two seasons we have a faint layer in our triple wall steel liner. It looks dark brown and black and flaky, but less than 1/10th of an inch thick and comes off easily. When wiping a finger through it the stainless surface shines through and the stuff is not tarry but just like soot dust. Problem is that cleaning is a huge chore because we have an insert. I would have to remove the baffle plate which only comes out after removing the secondary air tubes. Which only come out after removing their screws. Which, of course, won't budge a bit and are likely to break off if forced. Removing the whole insert is impossible considering that it weighs 1/4 ton or so. They don't design these new stove inserts with service in mind. Is it ok to just leave it like that for the coming season? Answer: The amount of soot that you describe is surely not in danger of igniting or causing any harm to your chimney. The creosote which ignites is like tar, and usually forms a shiny surface on the pipe which is almost impossible to remove with your finger or common tools. One thing to watch out for is elbows in the piping and/or other areas where soot which falls down the chimney might collect. So check on top of that baffle and any other place which might be a repository for soot.