This is my first year burning. Everythings been going well to this point but all that changed today. I was scooping out some coals on my wood furnace earlier today to make room for some wood. Seemed to be more smoke than usual despite my best efforts to minimize smoke (open the damper all the way and very, very slowly open the door) about a half hour later the smell of smoke was terrible.. So I ran downstairs and looked through the glass and saw no flame, then seconds later a HUGE flame and smoke bellowing out everywhere.. kept repeating.. no flame.. then huge flame and smoke.. Brain going a thousand miles and hour!! So i completely closed the damper and let the darn thing burn down for a few minutes.. seemed more like hours though.. So despite the smoke which was pouring out like crazy now.. I figured this was the best course of action. Eventually it cooled down enough and I emptied it out. The wood was black!! Very HOT and black as coal. I've been cleaning my heat exchangers and outlet tube every couple weeks and the cresote build up did not look that bad.. so I wasn't overally considered about what the stainless steel liner looked like. Looking back.. I think I dodged a very BAD situation!