The Washington Stove Works stove at our A-frame cabin works the first two or three days, and then QUITS drafting and fills the whole place with smoke. We're at 8500 ft. The chimney is 10" durapipe, some double wall and some single wall, with triple wall thru the main floor ceiling and again five feet from the top of the interior ceiling down. No horizontal bends or runs. We seem to notice it first when we have shut the front doors to the stove for the night. After the problem occurs, even after a few hours, we can't burn another fire.