Would love some input on this one folks. A lady I work with said her stove started belching smoke in the middle of the night, had to throw water on the fire and open all the windows, she was "slightly paniced" so I stopped by the house on the way home from work and was very suprised with what I found. She has an old "smoke machine" non EPA stove but it's in a rental property and she doesn't plan on staying, not the most efficient heat but helps cut down on her gas bill. I climbed up on the roof and found some very light textured creosote on the cap, not the sticky stuff, just dry & crumbly. When I took the cap off, about 18" down into the chimney (8" x 8" terra cotta flue) it was completly blocked off. I poked it with my finger and it just crumbled and fell apart. There was about 1-1/2" layer completely blocking the flue, but when I broke that out the rest of the chimney was pretty clean. Some powder & "crumbly" stuff on the sides, but impressively clean. No build up at all. Has anyone ever seen anything like that? What caused it and how does she prevent it from happening again. I ran a brush down since I was there anyway, but did not get much out at all. Any ideas?