Creosote, the black or brown residue of combustion that collects about the inner surfaces of a chimney flue liner, is highly flammable. If allowed to build up, it may possibly catch fire, causing cracks in "fireproof" brick, stone or clay flue liners and allow heat to succeed in nearby wood framing https://connernqlhy.tusblogos.com/28092465/ethanol-fireplace-things-to-know-before-you-buy