I'm still learning my Sirocco 30, this weekend I had the house warmed up and thought I'd turn it down and go for a long burn. About half an hour or so after turning it down I could smell a faint smoke smell upstairs that was noticeably stronger down stairs. I turned the stove back up about half way and the smell dissipated over time. Is this common or do I need to do something different or is it a draft problem on low? The chimney is 4' of double wall stove pipe inside, a double wall 90 with 1' of double wall stove pipe horizontal connected to 2' of class A though the wall, a T, then 18' of class A up the side.