Sometimes third degree creosote (a black, shiny, tarry, and highly flammable coating on the flue tiles) cannot be removed with a regular chimney brush. It requires a device that rotates chains rapidly to break up the glazed creosote. While this process does not harm tiles in good condition, it can cause previously damaged liners to separate. Rotary sweeps are generally necessary for third-degree creosote and/or direct connect installations. Our staff will be happy to discuss your specific questions, so just give us a call. And check out our glossary of terms page for more information.