Don't take chances with a dirty chimney and firebox - have a yearly cleaning! As you use your fireplace creosote deposits form on the fireplace and chimney walls. Under certain conditions, the creosote deposits can ignite, sometimes explosively, causing loud noises, flames and dense smoke. Other times, the chimney fire can be slow burning and impossible to detect. In either case, high temperatures are reached that can result in damage to the chimney structure and nearby parts of the house. See the youtube video below for what an actual chimney fire looks like - not fun!