A closed flue or clogged chimney is a simple fix but if your fireplace suffers from an integral design error, remedying the issue may be costly and time-consuming.
Flues and Dampers
The flue is the part of the interior if the fireplace responsible for air flow in and out of the fire box and the damper controls the amount of air allowed in or out. One cause of a smoky fire is a closed damper; if the damper is closed, smoke cannot escape up the flue and instead billows into the room. Opening the damper is a simple fix.
If the flue becomes clogged with debris like leaves or a bird's nest, the smoke may not be able to escape; cleaning the flue is essential for not only reducing smoke but also reducing the risk of a chimney fire.
If the damper is open and the flue is clear, smoke may still pour into the room if the flue is too cold. Warm up the flue by beginning with a small fire made from newspaper before adding your main fuel source.
Fuel
Seasoned wood is less likely to result in excess smoke than green wood. Smaller logs heat up more quickly and therefore burn off residue without producing excess smoke, whereas larger logs are slower to heat and may cause smoking.
Another fuel issue is the residue created by burning wood called creosote. Creosote builds up in the flue and firebox and if it isn't cleaned, it too will burn as fuel and cause smoking or, worse, a chimney fire.
Air
Oxygen is a necessary component to a fire but too much air circulating down the chimney due to wind will push smoke into the room rather than through the flue. A chimney cap reduces the effects of wind on your chimney and fire.
Another issue is indoor air pressure. The chimney draws air out of the room to pull smoke away from the fireplace. If an air-tight house does not replace the air taken by the chimney, it creates a low pressure area that pulls the smoke out of the chimney. Open a window near the fireplace to provide a different source of replacement air.
Design Error
If your chimney smokes all the time and simple remedies are not stopping the issue, your fireplace may have a design flaw. A common design flaw is that the chimney is too short and doesn't effectively draw the smoke away from the fireplace. A stone mason can add additional height to the chimney.
Another design error might be that the smoke chamber or the flue in your fireplace is too small, either by width or height. Replacing the parts is the only way to remedy the situation. If you suspect another design error, invite a home inspector or contractor to measure your fireplace to ensure that the proportions are correct.