Some fireplaces work just fine as long as you keep a rip-roaring fire going. But let it burn low, and it starts to smoke. (You might find that this type of fireplace is also smoky at startup, as discussed above.) The solution is to keep it burning high until spring, when you can open the windows… Just kidding. But seriously now, read on if your fireplace is okay during high-fire, but smokes as it burns low.