Common S2ENCE maintenance

The United States Department of Defense (DOD) uses a multi-tiered maintenance concept. Although there are some notable exceptions, the three-level maintenance concept is widely used. The three levels are organizational maintenance (O-level), intermediate maintenance (I-level), and depot maintenance (D-level). The various levels provide a separation of maintenance tasks based on their complexity, space required, personnel skill, and scope of responsibility. O-level focuses on the day-to-day tasks that are required by an operating unit to maintain operations. I-level tasks are performed in a centrally located facility with dedicated resources and facilities. These tasks often require specialized training and equipment. D-level maintenance supports O- and I-levels of maintenance by providing engineering assistance and performing maintenance that is beyond the capability of O- and I-level activities.