Was sleeping very well as usual when my pager tones out. Get to the station roll out the Sterling pumper and head to the call. Arrive on scene no flame in chimney. Since i was the first to show up with gloves i was volunteered to carry all the burning logs out of the house. Meanwhile others are on the roof with a chain down the chimney busting through the creasote. We get all the fire out of the insert pull out the insert and holy crap. Id bet they was a 5 gallon bucket of creasote behind that thing. The cresote on top of the insert had just started to catch up there were a couple of embers still smoking which is what was causing the smoke to come into the house. The whole top of the insert was about 1/2in thick in that stuff. The older lady tells me she burns dry wood and doesnt understand why so much creasote. Here is what i told her. The masonry chimney has no cap and ends at the insert. Any rain goes right down on the stove defeating the purpose of dry wood or evaporates on the way down still causing buildup as it goes back up. Maybe it wouldnt be so bad if it went past the stove to a cleanout but it didnt. You could see where wet creasote had run down into the fireplace and hardened.