The tear gas grenades being used to quell protestors in Egypt are actually made right here in the USA. They're intended to cause "tearing of the eyes" and "irritation of respiratory tract and mucous membranes". What's inside the tear gas?
Now, you probably didn't know this—because you're a normal human being—but kids apparently like to huff cans of compressed air. Boy, children are really high-tech these days. Back when we were small we stuck with markers, glue, and chalk, but now they're getting all futuristic with compressed air.