What process involves removing equipment from service?

Decommissioning refers to the process of taking equipment or systems out of active service, which often includes safely dismantling, disposing, or repurposing components. This process is crucial in various fields, including engineering, to ensure that all safety protocols are followed, environmental considerations are addressed, and that no residual risks remain from operational equipment.

In the context of the given options, decommissioning serves as an essential activity when equipment is no longer needed or is being replaced. It is characterized by a careful evaluation of the equipment's lifecycle and includes systematic steps to mitigate potential hazards once the equipment is out of service. This is particularly important in industries where safety and compliance with regulations are paramount.

The other options relate to the processes involving the installation, operation, or maintenance of equipment rather than its removal from service, which is why those alternatives do not fit the description of the process for taking equipment out of active use.