Dan

I have worked on many investigations related to property loss from spontaneous combustion of oily rags.  The following language has become standard label, SDS, use instruction language:

DANGER! Rags or waste soaked with any oil based finish have the potential to spontaneously catch fire if improperly discarded.

Immediately after use place rags or waste in a sealed water filled metal container away from buildings and other combustible materials.

Dispose of in accordance with local regulations.

I now recommend that the language not only be placed on the container label lid, but also on a piece of tape across the lid to force the end-user to read the warning before they open the container.  Destruction of the tape by opening the container is prima facia evidence that the end-user read (or should have read and had the opportunity to do so) the warning.

nl