Have been a few problems from time to time around here with cylinders. The tanks were mostly empty, on a cylinder cart and capped. He did not have the chain hooked. He lost it on the top step. The reason they know he did is because it either cracked the step or left a red paint mark on every single step on its way to the bottom of the door.
Some people think how their safety depends on the idiots they work with.
When carrying liquid nitrogen its better if it's covered and carried at thigh level. You don't want to spill it on sensitive skin or get it trapped between clothing. A section of REM makes sure that the contractors have the proper written plans, procedures and protocols. After that it is up to the contractors to make sure their employees follow the rules. Its their employers responsibility to make sure they do, not the University.