Why danger symbols can’t last forever

Chances are you wouldn’t be able to recognize a biohazard even if you were looking right at one. But the biohazard symbol? It’s pretty easy to spot. Most warning icons rely on previously established objects or symbols: a general caution might use an exclamation point, and a fire warning might use an illustration of a flame. But the biohazard symbol references an idea that is much harder to picture — and in the 50 years since its invention, it has become one of the most recognizable icons on the planet. But can the meaning of a symbol like this last an eternity? A special Department of Energy project is trying to figure that out.