Ever since I had my Morso 3660 installed a few years ago we've taken the wintertime coldest room in the house and turned it into the warmest room in the house and dropped our oil consumption by about 75% per year. But one thing has always bugged me...every time I open the stupid door on the stove to feed it, I always get this belch of smoke that sometimes pours out into my living space. Didn't make sense...my chimney is a straight vertical shot, a good 18-20 feet indoors (very high cathedral ceiling above the stove) of double wall black pipe and then another 12 feet of triple wall metalbestos where it approaches and penetrates the roof and then it goes a good 2 feet above the peak. Most of it is indoors, the house is on a hill...just doesn't make sense that the draft on this sucker isn't pulling dust bunnines across the floor from the wind it makes. I tried opening the windows to equalize the air pressure, even went so far as to open the walk out basement doors and then open the door at the top of the basement stairs, the height delta between the basement and chimney cap is about 40 feet or so...still get smoke inside which hurts our air qualitya nd gets everything dirty. So this year I'm cleaning my chimney and I get it all hoovered out and back on the stove and I look up and see each and every joint on the double wall sections has dust and grey soot hanging down out of almost the whole joint, all the way around the chimney. I get up on the ladder and vacuumed them out and then while I've got a small fire going I put a lighter at full blast near it...the wind getting sucked into the chimney at each joint was strong enough to make the flame go sideways 90 degrees and then snuffed it right out. So I let the fire die out and sealed each joint with some stove gasket in a caulking tube. New fire and its amazing! I get no smoke coming out of there now. So hooray for me! Now I have to wonder, since I've probably doubled the draft in my chimney, I'll probably pick up some extra heat...wonder if I'll gain efficiency too?