You don't say what smoker, but GQUE is correct. After a period of not being used, the layer of grease/fat built up on the inside top of the smoker flakes off and can drop on the food the next smoke. I find this happens more in the winter. I also wipe down the top surface with a damp rag just to remove the flakes of grease that will discolor the next product. Definitely not a health issue, but not appetizing.