Cleaning intervals are based on usage. The more wood burned the more creosote accumulation within. It is recommended to sweep your wood-burning chimney after every face cord of wood burned. The NFPA (National Fire Protection Association) code 211 says, “Chimneys, fireplaces, and vents shall be inspected at least once a year for soundness, freedom from deposits, and correct clearances. Cleaning, maintenance, and repairs shall be done if necessary.” Annual inspection with a fireplace chimney sweep as required. This is the National safety standard!