In this week's Colin's Classroom, i visited the Duluth Children's Museum to show them a simple science project they can make at home! All you need is a cylindrical container like an oatmeal carton, some saran wrap, and a pair of scissors. 
The fog machine was just a bonus to show what was happening!
Colin, "What we have here is just a standard little oatmeal carton."
"I'll cut a small little ring all the way around."
"...and use the air inside and do a really cool little trick with the air where you can actually make these little rings that float through the air."
"One side has a tight seal, that saran wrap, on it just like this. And then that other side, I actually cut a small little hole in there, right?"
"And fill this up with a little bit of smoke. And I should just be able to go TAP. You guys see that? You see these little smoke rings? Just like that. Do you see how these little rings just come popping out of there?"
"If I hit it soft enough you can see these small little rings that show up. Here! Right towards you! Right towards you. You see it? Right towards you. And what this is, this is literally just a little bit of air that's shooting out."
"Look at all these! There! There's a good one!"