Argh. You can't just post that without giving out the juicy details
To make up for not knowing those details, here's my small rack-mount UPS story.
Somebody ignored the UPS replace battery warnings, and the battery pack swelled up a lot. It forced the sides of the UPS case outwards a few millimeters which was enough to make it completely impossible to slide the UPS out of the rack on its runners, and also completely impossible to slide the very important server immediately above the UPS out of the rack.
The idea of leaving the UPS there "forever", turned off and disconnected, until the entire rack was scrapped, was given some consideration. But the thought of a high-pressure acid leak in the vicinity of much expensive hardware was too disconcerting. As was the (lack of) gravitational stability of a rack with many kg of UPS near the top and the chances of doing one's back an injury in getting it there.
It took several hours downtime. We had to poweroff everything in the rack. Then we had to remove servers one at a time, starting at the top, until the one immediately above the UPS was able to move a few millimeters upwards and unbind itself from the body of the UPS. Then there was lots of poking and twisting and prodding with various tools down the very restricted spaces between the UPS and the rack until eventually, it was made possible to extract it using brute force. Then we had to reassemble everything in the rack, this time with a 1U gap above the replacement UPS "just in case".
No, the old UPS didn't explode. Not even when a colleague was kicking it hard from behind to force it forwards a few millimeters at a time, while others held on to the rack.