A closed system, in blood banking, is a blood container or collection process in which the sterility of a blood product is not compromised. We often use the phrase when a product is manipulated using equipment that allows the product to remain sterile, such as when sterile connecting devices are used to combine multiple units of platelets or cryoprecipitate into one “pooled” product. Closed systems are important in blood collection centers because their use allows pooled products to keep their normal expiration time (shelf life). The opposite of a closed system is, of course, an open system.