I have a 22 year old Franklin stove that meets the EPA standards with a 21 foot exterior rise. The last couple of years when lighting the stove, i.e. the stove is still cool smoke come out below the ash pan. The smoke and heat are exiting the burn area as normal, but smoke comes out from some the bottom, not the opened door. I wonder if something in the system has become clogged. By the way, after a minute or so when the fire begins to heat up this problem ceases. One more bit of information. This happens even when the outside temps are not extreme. I know better than to try to light the fire when the cold air in the exterior rise is too cold for the slightly warm air to overcome it.