An open system, in blood banking, is an environment in which the sterility of a blood product cannot be guaranteed following manipulation. For example, when blood products are washed, deglycerolized, pooled, or otherwise manipulated in an open system, the shelf life of that product is automatically reduced to either 24 hours (for products stored at 1-6C) or 4 hours (for products kept at 20-24C) because of the possibility of bacterial contamination. The opposite of an open system, not surprisingly, is a closed system (in which the shelf life of manipulated blood products does not change after that manipulation).