I think others were having the same problem, just wanted to mention it here on what to do. If I partially close the damper I see smoke coming out by the top corner near the door hinges. Also I noticed that on the bottom seal there is only one clip that looks like a nail. It does not stay in the hole. So the bottom seal just hangs and appears to turn when you try to close the door. I think air is getting in through the bottom. I bent the nail the opposite way and it is stayin in for now, but half hangs down too low. I guess I should call for a replacement door.