According to the Chimney Safety Institute of America, a chimney should be cleaned whenever soot covers surfaces inside the flue system. Because the process of inspecting a chimney requires specific skills and expertise, a certified chimney sweep company such as Chim Chimney: Professional Fireplace Services, Inc. is recommended for all maintenance and cleaning tasks.
When a glaze is noticeable in the flue, the surfaces must be cleaned immediately. Glazing is dangerous because it is highly combustible. If a lot of creosote and soot build up around the glaze, a fire may start in the chimney.