I probably have close to a hundred hours of smokes on this smoker. The last time or two I am starting to have a soot buildup.. I have a 10 inch cast iron pan in the original wood pan. When I went to dump the ashes I had a quarter of a inch or more of soft powdery soot on the bottom of it. It came off extra easy with a paper towel. I checked the flame & it was a blue flame with a inch or two of yellow. That bottle was almost empty so I switched bottles. Hopefully that was all it was. I have only had this smoker for a month or two so any help or ideas would be appreciated. Thanks Phil P.S. The taste of the food has not been changed by this..