CORe

Compact Oxygen Rebreather
The CORe was first invented when oxygen tanks became insufficient for extended lunar traversing.

It operates by scrubbing the carbon dioxide from the user's breath and then converting it back into pure oxygen through an electrochemical redox reaction. High pressures are involved to maintain the a small volume. Although extremely rare, a violent decompression can occur if punctured. Unfortunate souls who happened to be wearing a CORe during this event often suffer severe facial lacerations.