+1...More often then not I'd say down. Down will be safest MOST of the time but it will also depend on your environment. Bear in mind that some surfaces will cause a ricochet if a discharge was to occur, although firing into the air will ALWAYS lead to a bad situation as the round is going to have to land somewhere and when it does the bullet will be just as capable of killing someone as when it was originally fired.
What is the "safe direction" ?
(Other than downrange.)
Agreed. Still I prefer up, while it may not be safest under all circumstances I find it to be more expedient.It is so situationally dependent that it isn't even funny.