Depending on who you go to, some places will not sell you tanks of Helium. We did a balloon launch expecting to use Hydrogen because Helium was going to be problematic. The sales rep at the supply place took a look at the group of us knuckleheads with absolutely no Hydrogen experience and ended up selling us the Helium while also exchanging all of our connectors. Hydrogen tanks use specific connectors different from all other tanks to make using a hydrogen take by mistake very difficult. I was nervous about using hydrogen and had no issue with the higher price for the helium knowing I wasn't going to catch on fire.