In-game description

"Combines with O2 to make WATR."

Reactions

When Hydrogen is met with O2 and set alight with FIRE, it burns into WTRV. Hydrogen has no effect on pressure and can come in contact with QRTZ at sub-zero temperatures.

Fusion

When Hydrogen is at 50 pressure and heated to 2,000 degrees, it will transform into PLSM and release one NEUT, one yellow PHOT, and generate either one or two particles of NBLE. It will also generate 50 pressure and raise the surrounding temperature to 4,000 degrees.

Since NEUT and ELEC transmute to Hydrogen, the process may self perpetuate.