So the other night I heard quite the air whoosh sounds coming from my chimney. Being the newer owner I am I freaked a bit thinking maybe I had a minor chimney fire. I inspected the chimney today after letting everything cool down and nope, not any creosote anywhere or evidence of a fire. Just a very fine layer of white ash everywhere. So I started her back up after a good cleaning. Moral of the story, don’t freak out over every new sound. The double wall collar is quite the air whoosh noise maker.