In my opinion, the size of the spill is less of a determinant than the ability of the responder to protect themselves from exposure to the material spilled, especially from inhalation.  I find that most lab researchers are pretty aware of liquid contact, but usually overlook the inhalation hazards.  Thus, if it can’t be cleaned up in a few seconds with a few paper towels and the cleanup supplies moved to a hood, it’s probably better to bring in someone who is trained to use the appropriate respiratory protection.

At my company we put a 4L limit on spill cleanup in general (for anything other than water or benign aqueous spills), since people can’t determine %LEL without a meter.  However, we also ask people to call for help for smaller spills where they can’t protect themselves as outlined above.

Steve Arvedson