I've been looking for this video for months! My close personal friend™ Adam Savage showed this to me a while back, and I've been dying to post it here, but didn't see it on YouTube until yesterday (linked from Wired). I laughed myself silly when I first saw it, and I'll readily admit I cracked up watching it again just now. Man, it's funny.
He warns people not to do this at home, but sulfur hexafluoride is evidently really expensive, so it's not that big a worry I think. But wow, I'd love to try that. I'd probably scare the crap outta my dogs.