I've been reading a multi-page article in my IAEI News about multimeter accidents, injuries, and deaths from multimeter misuse (or using the wrong multimeter in the wrong location).
This is the gist of the warnings: If the multimeter you are holding fails for any reason (could be operator caused, could be age, deterioration, moisture, etc.) there is a good probability that the multimeter failure acts as a short across whatever you were measuring - with one lead connected to one side, the other lead connected to the other side, the meter fail and shorts out ... you might as well be holding a piece of copper wire between the two things you were measuring.
That short can lead to an arc or arc flash, burning your hands, clothes, etc., not trying to be scary of anything, but there have been many, many, many cases of such happening.
The meter you use needs to have the correct CAT I, CAT II, CAT III, or CAT IV rating for the area (not just what you are measuring, but what is around that area and what is supplying that area).
Here is some good information, descriptive drawings, and examples of the different CAT areas in which different CAT rating meters should be used.
http://www-group.slac.stanford.edu/e...ter_Safety.pdf
and
Anatomy of a high quality meter
Most of what we would normally check would be CAT II or CAT III, however, many of us stray into CAT IV (basically when you use your meter outdoors to measure the things we might measure)