I think the average percentage a shredder assumes is fluff in thin is about 35%. Also that fluff is usually transported to an industrail landfill to use as cover, which costs the scrap yard. You have to pay to have that stuff hauled off. I just had a customer yesterday that was bringing in loads of white goods, a few a day, and they were disposing of their trash in the same loads. We just satared doing business with this compnay, and we just stopped doing business with them on the second day. We dont want trash. We are in the bsiness of buying metal, not wood, not trash, not water, etc. A lot of people try to take advantage of the fact that some wate products are factored into the price by throwing everything thing they find into the tin category. Yards have to be very diligent about grading material. As for clean steel, #2 HMS is steel under a 1/4" thick generally, and #1 HMS is 1/4" and thincker.