Hou have my apologies, sir. It seems that I was the one making a fool out of myself. Amazon is apparently using liquid hydrogen in some of their operations. I am never afraid to admit when I am wrong.
The warehouse I worked at used liquid hydrogen on all of the OPs, short for Order Pickers. They are wire guided lifts that you ride in, and they go in the narrow isles and go up to any level top to bottom. So you can pick items or put them away, called stowing. The wire guide is computer controlled so once you go into an isle and pick up the wire guide, sort of like an ‘electric eye’, if you will, it can’t be steered anymore by the operator and you can’t crash into a rack on either side, they can only go straight through the isle and up and down controlled by the operator. There’s only about 8 to 10 inches clearance on either side of the OP but it still can’t crash and can go pretty fast straight forward and up and down too. Quite cool really. Backing up an OP is strictly forbidden, especially when inside an isle of racks.
I also worked at another Amazon warehouse for a while not too far away in adjacent city, it had the same type of equipment. OPs and other, but that one used all electric equipment, there was no liquid hydrogen in use at that warehouse.