Does every hazardous situation need a safety sign?

Does every hazardous situation need a safety sign?

It is a common myth that every hazardous situation requires a warning sign.
Warning signage  is useful when there’s a major hazard that is also being controlled in other ways -  as an additional control.
But that doesn't mean you should add a sign for every trivial hazard.  In fact, using too many signs means no one will take much notice of them.

Source: UK HSE, 2007.
And where there are major hazards you should never just rely on warning signage - take practical steps to deal with the hazards using the "hierarchy of control".
If you do need a sign, make sure it is correct for the hazard and that it is clearly visible.