Using too many signs just guarantees no one will read any of them.
Safety signs are useful when there's a significant risk which can't be avoided or controlled in any other way. But that doesn't mean you should add a sign for every possible risk, however trivial.
Where there are serious risks in your workplace, don't just rely on signs - take practical steps to deal with them. If you do need a sign, make sure it has the right symbol and is clearly visible.