First this is the second time in 3 months that I checked the cat and basically no fly ash or dirt or anything. Checked stove pipe and looked into chimney and basically just a touch of creosote - just a little on the side and when I say little almost nothing. Looking at the terra cotta chimney there is a little black on it but not like it has a bunch of crap hanging on the sides or anything - whistle clean from what I have seen in other pics posted on here. I am still thinking though about lining it with a insulated ss liner this summer to just improve performance and since it would probably help the chimney last longer