@tony @Porcia @quixoticgeek Vacuum person here.
I in no way believe that hydrogen is the answer to energy demands, it's just a thing put up by the dying fossil fuels industry but we normally test for leaks with Helium. It's the smallest thing that's easy to detect for leaks. On paper, Hydrogen is smaller so could leak more but Hydrogen normally comes as H2 so the molecules are bigger than helium in its natural state.
And hydrogen embrittlement is definitely a thing. Hydrogen power is a scam