Hydrogen safety my chance to mention the BRT at the lab. They had a hydrogen bubble chamber with something like 400 gallons of liquid hydrogen in it. They had a emergency drain valve on the bottom that drained into a special sewer underground that ran by gravity to the top of the BRT just downhill. The hydrogen was at a critical temperature so any particles going through it would form bubbles that could be seen and tracked. Probably just under boiling point?
Any way. The brt was a 20' diameter sphere filled with old aluminum cans, squashed flat, as a heat sink so the liquid would vaporize and be flared off if needed.
BRT= Big Round Thing.
Bil lD