Every time you use your fireplace, creosote is created and deposited on the inside of your chimney. How? As smoke travels up the chimney, it cools and deposits this organic substance on your chimney liner. As that substance cools even more, it solidifies and results in a caked on substance that will build up use after use. Creosote is made up of particles from the wood and is incredibly flammable. After enough creosote builds up, it can ignite and launch a fast-spreading, dangerous chimney fire. Proper chimney sweepings performed by a CSIA certified chimney sweep will remove this creosote and leave your chimney and fireplace system clean and ready for use.