Q: What is level 3 creosote? I have an 80 year old home that was a longtime rental house. I have lived here five years and have been using the fireplace for four of those years. I do not know how long it has been since my chimney was swept (potentially decades, if ever). I just had a chimney sweep at my house and he informed me that the creosote in my chimney was quite thick (he used the term “level 3” creosote). He also said that in the smoke chamber, the brick is stepped (instead of smooth) and that there is a lot of dangerous buildup in there. He recommended two applications of an acid cleaning (which he said are not entirely foolproof, and work better above 45°F) and that we use a chemical when we burn our fire to help “chalkify” the creosote buildup. He showed me the buildup inside with a light and everything he said seemed to make sense. Does this sound like it’s on the up and up? I can’t find any info on this acid cleaning and I would like to know if this sounds like it is the proper course of action in a case like mine.
What you have described sounds pretty typical. In addition to the chemical treatment that you mentioned, professional-grade chemicals, usually in the form of a powder, can be applied by chimney sweeps to help change the nature of the glazed creosote to a form that can be removed by a professional with a brush Both forms of these products require some heat such as you would find in a small fire in the fireplace.
If the creosote is gummy, about the only way to deal with the creosote is with a chemical treatment or with an acid application. Acid applications are not as commonly used since they are harder to apply and have to be neutralized a few days after application. If the creosote is crusty or fractures when hit (as opposed to gummy) a rotary cleaning can be helpful. Read our position statement on chemical chimney cleaning products here.