Yeah I finally cleaned mine this spring for the first time since we've lived here (almost 10 years). Ash blew out of the open port in the chimney where I had just removed the connector pipe for the stove, and covered the stove ... and everything within 10' of it with a half inch of super-fine flour like dark grey powder. A combo of flyash & oil soot. Nice!
Looked just like those moon pics you see with Armstrong's footprint. I was making prints just like that all around the basement. What a mess! But the chimney is now pulling a .02 at 80° outside, cold! BIG difference. Had to re-adjust the baro after that - thing is constantly open now even on the hottest days.