GETTING A SMOKY FIREPLACE TO WORK RIGHT
There are basically three problems that will cause a fireplace to smoke. They are Downdrafts, Lack of Air, and a cold chimney.
1. The lack of air for the wood's combustion is a common cause of a smoky fireplace. A simple fix is to slightly open a window to allow airflow.
2. A cold chimney can cause smoking. This usually happens when you first light the fire. There can be a lack of good draft due to the chimney being cold.
To stop this problem, light a sheet or a couple of rolled up newspaper pages before you start the main fire and hold it up to the damper in the chimney at the top of the fireplace. Drop he paper before you burn yourself, and start the fire in the fireplace. Burning the paper can heat the air. This could help create a good updraft.
3. If you light the fire and the fireplace smokes after the fire is burning, then downdrafts could be a problem. Downdrafts are caused by cold air coming down the chimney from outside. This forces smoke into the room.
Your chimney may not be high enough above the house to prevent back drafts. It has to stand at least 3 feet above the highest point of the roof or other structure that's withing 10 feet of it. Don't let tree branches overhang it within that distance.
Your fireplace opening may be too large for the flue to handle. Here is a simple way to find out. Cut a piece of plywood that is wider than the opening across the top of the fireplace.
Wet the plywood and hold it across the top of the opening of the fireplace. Lower it slowly over the opening until the smoke stops. Be sure to cut it wide enough to hold it without being burned or uncomfortable. To make the fireplace opening smaller, stack one or more layers of firebrick on the bottom of the fireplace. This will reduce the size of the opening.