IIRC, the Hindenburg had diesel engines turning the propellers. The hydrogen was contained in several "gas bags" inside the fuselage to provide lift. The skin of the fuselage was painted with a volatile aluminum acetate paint which burned along with the hydrogen.
What happens if you get rear-ended?
If you are asking about what happens to the hydrogen, not much. The tanks are probably as strong as propane tanks in the beds of pickups or under vans. If there is any leak, the gas is lighter than air and will rise. Unless the cabin of the car fills with a hydrogen/oxygen mixture and explodes from some spark, there's no real prolem.