Two words, exactly
On this page11
The labeling requirement supplies the words rather than the fact
Containers and aboveground tanks used to store used oil at generator facilities must be labeled or marked clearly with the words Used Oil.
Labeled or marked is a deliberate pair
A painted stencil, a stamped plate, a printed label or a marker pen all satisfy it. The rule cares that the words are there and legible, not how they got there.
Clearly is the only qualifier
No type size, no panel, no color contrast, no position. Which is the loosest presentation requirement of any labeling rule described across this library.
A few rules here supply exact wording and this is the shortest
The textile trimmings rule gives exclusive of decoration and exclusive of elastic. The care labeling rule gives no bleach, do not bleach, and only non chlorine bleach when needed. This one gives two words.
And it attaches them to something that is not a container
Fill pipes used to transfer used oil into underground storage tanks at generator facilities must be labeled or marked clearly with the words Used Oil.
A label requirement on a pipe is worth stopping at
Across this library labels attach to packages, to products, to panels and in one case to the inside center of a garment neck. A fill pipe is a route rather than a thing, and labeling the route is a different idea.
The reason is clear once the failure mode is named
A pipe is where the wrong fluid gets introduced. Labeling the tank does not help somebody standing at a fill point with a hose, so the words go where the decision is made.
Which is a principle other label rules apply in their own way
The care labeling rule orders the information onto the outside of a package when the package hides the garment label. Both are the same move: put the words where the reader will be.
And the words themselves carry the whole message
Used Oil says what is in the container and, by saying used, that it is spent rather than fresh. Two words doing a classification and a condition at once.
None of which applies to anything on this shelf
No container here is used to store used oil and no page says any of them may be. The requirement is described because it is the labeling half of the spine.