In my uni days it used to be the favourite practical joke to tie up a small baloon with a fuse string and let it float to the ceiling. It sits there with the fuse string slowly smouldering for a couple of minutes and after that BOOM.
So yeah, hydrogen? safe? Bollocksssss... As far as helium, its cost limits it to exotic applications.
The only real way to build an airship is to have it nuclear driven. Heat up air with spare heat from the reactor and use nuclear power for propulsion. It limits the size to be at least half a mile in length, however you can lift and carry any amount of cargo from anywhere in the world to anywhere in the world in a couple of days. No more container ships, no more containers on railways and much less road trailers. And the bigger it is - the more efficient.