Power Symbols:  Do They Work?

We use a variety of words and symbols in everyday life to communicate useful or important information, such as:

While not perfect, they help avoid much injury and inconvenience.

Do you recognize the symbols below?
Do you know what they mean?

You probably see most or all of these on a regular basis, but don't pay a lot of attention to them.

If we don't get much meaning from these, why have so many symbols?