Creosote is a byproduct of burning wood. The amount of creosote depends mainly on the type fuel (wood) being burned, the moisture content of the fuel and the performance of the chimney and it’s connected appliance. Burning green pine wood is known to create creosote. When creosote builds up in the flue or on the cap it can reduce the diameter of the flue pipe and/or openings of the cap causing a full or partial blockage of the chimney. A blockage will cause smoke to back up into the living area, increased residency time of smoke in the flue which will exacerbate the problem, causing more smoke and more creosote.