Talking and singing inside a giant helium balloon

It's fun to breathe in helium from a balloon to talk in a high voice, but you only get to do it for one breath. However, you can breathe in an atmosphere that's 20% oxygen and 80% helium indefinitely.  (The nitrogen that makes up 80% of the atmosphere serves no function to living organisms, so it can be replaced with an inert gas like helium),  Thus, you can spend a good quarter of an hour giggling in funny high voices while sitting in a small chamber filled with this air.

A co-worker told me that scuba shops can give you a tank of compressed gases in any proportion you want... so I quickly ordered up a custom atmosphere optimized for silliness.  I made a giant airtight balloon out of a king size mattress bag, which was big enough to hold two people and the tank.

Here are the results: 

The video contains some mild language and a lot of silly voices but is otherwise SFW.

FOR SCIENCE!