Generating hydrogen is very easy, there are numerous acid+metal and alkaline+metal processes that aren't expensive or use anything like rare materials. So as lo

Generating hydrogen is very easy, there are numerous acid+metal and alkaline+metal processes that aren't expensive or use anything like rare materials. So as long as the exposure is such that explosive risks are minimal, it's a good option for lighter-than-air needs. It's not, of course, much of an option for cryogenic processes where helium is required.