Sweeping the chimney and performing an annual inspection is the most important part of maintaining your fireplace and chimney. Over time, the chimney can become coated with soot and creosote, which are byproducts of fires that aren’t burning efficiently. Once the coating builds up enough, it can potentially catch fire in what is known as a dangerous “chimney fire.” Eldridge explains why a chimney fire can be so destructive: “While the firebox is built with firebrick and intended for direct contact with fire, everything above the damper is designed to withstand only hot smoke and gases from the fire, not fire itself, so a chimney fire can cause serious damage.” The chimney should be swept when creosote build-up is 1/8-inch or more and at the end of the season. The sweeping should be done before summer, because humidity in the air can combine with creosote to form acids which can damage masonry and result in strong odors.