Feed lines. Whether feeding the machine from the drying hopper, gaylord, or bag, it is critical to ensure that all of the material has been cleaned out. This is usually as simple as removing the feed line and allowing the vacuum loader to suck all of the material out of the feed lines. There have been cases were the material handler does a nice job of cleaning everything out but forgot the feed lines and when the new material was introduced all of the previous material was pulled in with it, contaminating the material.