Why a Fireplace Smokes

Symptoms

• When you use the fireplace for the first time in the fall or early winter and the smoke doesn't go up the chimney, check the damper -- it's easy to forget to open it again. Then check the flue, as it may be clogged and not allowing enough smoke and gas to escape. Temperature fluctuations between indoors and outdoors may cause a reverse chimney flow and force air back down. Also, strong wind currents may force air back down the chimney, creating a downdraft.

Wood

• Unseasoned firewood can cause smoking problems. Hardwood such as oak, cherry, beech, hard maple, walnut, dogwood and ash are good firewood when prepared correctly. Softwoods such as cypress, cedar and redwood also burn cleanly; however Douglas fir and pine burns well but can tend to be smoky.

Chimney Design

• A properly designed and built fireplace should not smoke. Occasionally the chimney may be too small to accommodate the size of the fireplace. The flue on the chimney is a crucial -- if the flue is not adequate for the type of fireplace, you are going to have problems. Two-sided fireplaces that open into two rooms are also prone to smoking due to the size of the chimney and varying air drafts.

Air Pressure

• Sometimes simply cracking a window will prevent fireplace smoking. Homes that are more air-tight possess different air pressure inside that may combat with the air pressure outside. That has the potential to impede air from drawing up through the flue properly. Opening a window slightly alters the air pressure enough to allow air up through the chimney and prevent smoking.