I have a Legend outdoor coal furnace and had a smoke problem that was drifting back into the hopper and causing condensation enough for it to ice up around the auger and cause the auger to snap in two. The smoke would only come back when the machine was running. We found a solution to keeping the smoke out of the hopper by installing a 1 1/2 inch air tube that went from the blower box situated under the hopper and went up into the top of the hopper. When the blower starts up air goes up the tube and blows air into the hopper which pressurizes the hopper and forces the smoke back into the firebox where it belongs. This has worked very well and now the hopper is dry, no sign of any moisture or ice. We installed it with a valve so we could adjust the airflow, however it seems to need all of it to work properly. If we did it again, I would use a 2inch pipe instead with a valve.