The "chemical space" of all possible organic chemicals is large and increases exponentially with the size of the molecule. Most chemical libraries do not typically have a fully represented chemical space mostly because of storage and cost concerns.
Because of the expense and effort involved in chemical synthesis, the chemicals must be correctly stored and banked away for later use to prevent early degradation. Each chemical has a particular shelf life and storage requirement and in a good-sized chemical library, there is a timetable by which library chemicals are disposed of and replaced on a regular basis. Some chemicals are fairly unstable, radioactive, volatile or flammable and must be stored under careful conditions in accordance with safety standards such as OSHA.
Most chemical libraries are managed with information technologies such as barcoding and relational databases. Additionally, robotics are necessary to fetch compounds in larger chemical libraries.
Because a chemical library's individual entries can easily reach up into the millions of compounds, the management of even modest-sized chemical libraries can be a full-time endeavor. Compound management is one such field that attempts to manage and upkeep these chemical libraries as well as maximizing safety and effectiveness in their management.