creosote

Creosote is a tar-like, combustible substance formed when smoke from burning wood or coal condenses and accumulates inside chimneys or flues. It consists mainly of various chemicals, including tar, tars, phenols, and polycyclic aromatic hydrocarbons. Over time, creosote builds up, creating a sticky, flammable layer that increases the risk of chimney fires and indoor air pollution. Regular inspection and cleaning of chimneys are essential to prevent creosote buildup, ensuring safe and efficient operation of heating systems.