MODEL RELEASED. Preparing blood units. Laboratory technician using a barcode scanner to register the mixing of donor blood components. The process is called component pooling. Donor blood is separated into its components for more efficient use of the blood. The red blood cells (which carry oxygen), the platelets (vital for clotting) and the plasma (the liquid component of blood containing numerous blood proteins) are all used in different ways for different blood disorders. They are often mixed back together again to produce the optimum mix of blood components. The properties of the components must match, such as the blood groups, to avoid any complications, and careful records must be kept.