Which of the following is not a reason for equipment turn-in?

The option indicating "upgrade" is not a reason for equipment turn-in because the process of upgrading generally involves replacing or updating a piece of equipment with a newer version or model rather than returning it. Upgrades typically mean that the existing equipment is improved while remaining in service, not removed or turned in as obsolete or no longer needed.

In contrast, the other choices represent common scenarios where equipment turn-in is warranted. A transfer occurs when equipment is moved from one unit or location to another without necessarily being discarded or decommissioned. Donation involves giving away equipment to an entity that can use it, while disposal denotes the end-of-life phase where equipment is permanently retired and disposed of appropriately. Each of these options entails a definitive action resulting in the equipment no longer being in service at its original location or unit, whereas an upgrade holds onto the equipment for continued use.