SearchResearch Challenge (4/25/18): What do these symbols mean?

Symbols are supposed to be easy.  

The idea, after all, is that a symbol works across languages and let you glance at it, immediately understand what it means, in order to rapidly understand what's going on.  

In general, it's good to be able to know what the symbols mean (in case you really need to take action).  It's good to know that this means biohazard:  

But in my experience, I see all KINDS of symbols that I don't understand.  So, here are a few symbols I've found in my travels this past week.  Can you tell me what they mean?  I don't know if they're important or not... which kind of defeats the purpose!  

1.  This blue cross (it really IS blue) with a stick and a snake that I found on an inside wall:  What does it mean?  Where would you normally see this?  How important is this to me?  Here's a photo I found in a building:  

2.  Here's another symbol--a box with arrow.  The only clue I have about this is that it was in a parking lot... on the ground, shown on top of a plastic traffic dot that's cemented to the ground.  What does this mean? 

3.  And lastly, a symbol that I've found on the side of a few walls in the city.  What could this possibly mean? 

As always, tell us HOW you found out the meaning of each.  Are they important symbols?  (Meaning, do *I* need to know about them in the course of my daily life?)  

Search on!