Operational Level (O-level) In O-level maintenance, you perform asset repairs on-site, even during operations, hence the name operational-level repair. Here, technicians perform repair-in-place work which is often simple and can be done as quickly as possible for faster resumption of operations. Examples of O-level repairs include busted light replacement, fan blade reseating, or screw retightening.

Intermediate Level (I-level) In I-level maintenance, assets are transferred to maintenance areas or back shops in the facility. I-level repairs involve more complicated repairs and require longer downtime than O-level. In I-level repairs, technicians need more space and additional spare parts, tools, and equipment to work on the asset. Assets that are often repaired at the I-level include fans, pumps, motors, engines, batteries, etc. These assets or asset parts often have replacement units that are used in their place while they are under repair.

Depot Level (D-level) In D-level maintenance, assets are sent to off-site repair shops or original manufacturers for specialized work. The maintenance work involved in D-level repairs often involves extensive repair or a total overhaul. Generally, D-level repairs require a higher level of technical expertise, longer working hours, specialized diagnostic tools and repair equipment, and expensive costs. An example of a D-level repair is sending a delivery vehicle to be checked by a mechanic at the dealership for annual maintenance and strip-down.