There are numerous reasons why a fireplace smokes: the chimney system is not high enough; the chimney is too small; there is a blockage or restriction in the chimney; the wood is too wet, not properly seasoned; the chimney is on an exterior wall and presents a cooling effect which will reduce the draft; trees or buildings surrounding the chimney can affect the wind, so backdrafting can occur; tightly sealed and well-insulted homes can create a negative pressure within the home causing smoke problems due to insufficient "make up" air supply.