Cross-contamination is the contamination of one oil grade or type by another grade or type (e.g., between olein and stearin, between palm oil and palm kernel oil, etc.). This cross-contamination between different grades and types of oils and fats will affect the quality specifications, such as iodine value and melting point. This will in turn affect the intended use of these oils and fats since they cannot be used in the products that they are intended for. For refined palm oil products, contamination with crude products or with lauric oils is considered bad. This cross-contamination of the oil is also due to negligence, bad handling, or faulty equipment and tanks. In addition to cross-contamination between different grades or types of oils, the practice of not cleaning storage tanks regularly or between uses may cause contamination of the new consignment of oil by rancid residues left in the tank. This can affect the quality of the new oil in the tank. Commingle of oil consignments in ship tanks can also be another source of cross-contamination