Creosote, the black or brown residue of combustion that collects over the internal surfaces of a chimney flue liner, is highly flammable. If allowed to Develop up, it may possibly catch fire, triggering cracks in "fireproof" brick, stone or clay flue liners and permit warmth to achieve nearby wood framing and https://gas-fireplace23119.blogocial.com/not-known-details-about-chimney-64204890