Sorry for being so late with this. I had exams and such, and I wasn’t exactly in a good mood either.
Anyway, in Rad & Skit’s world, people simply can’t be around helium gas at all. For some reason, exposure to helium causes undesirable reactions… chemical, physical, psychological or emotional, I don’t know, but from the looks of it, I don’t think it’s pretty! 
The balloon parade itself was inspired from a group of friends, well, parading with balloons, whom I saw on my way out of school to the bus stop. I think they were celebrating a birthday or something.
No, I have not seen Up yet. I hope to someday.