Storing frozen blood products. Boxes of labelled donor blood products in a freezer to preserve them for future use. Donor blood is filtered and then separated into its component parts to ensure more efficient use. The main components are red blood cells (erythrocytes), platelets (thrombocytes) and the liquid component plasma. The white blood cells (leucocytes) are rarely used and they are normally removed by filtration to avoid complications. The freezing process is complicated, as damage to the blood cells must be avoided. Some of the active clotting components in plasma can be preserved for 1-7 years. Treated red blood cells can be frozen for up to 10 years.