One time, me and my dad filled a big trash bag with helium. Then we duct taped the end shut; obviously not airtight. But when we let it go it went so high that we eventually lost sight of it.
Also, my nephew sent up a balloon with a message tied to it from school one day where they live in Butler, Mo., and a few weeks later he got a letter from someone in Illinois who found the balloon and replied to him.
This also reminds me of the guy who tied a bunch of large helium filled balloons to a lawn chair, strapped himself in and took off. He reached upwards of 12,ooo feet elevation, and actually caused the air trafic controllers at LAX to divert planes because he was in their flight path. He eventually returned to earth and lived to be arrested.

be good.