The  “ passive-assisted “ (PA) carbon dioxide scrubber and dehumidification system uses chemical absorbents, and requires two watts of DC power per occupant. This very low power requirement is possible because chamber gas is moved across two-sided beds of absorbent at low velocity rather than being forced through the absorbent beds. On-board carbon dioxide, carbon monoxide, and oxygen monitors are equipped with flashing light and audio alarms, which are activated when the respective gas pressures fall outside preset levels. Variable voltage, fluorescent reading and local area lights use 3-8 watts each. A bank of absorbed glass matting batteries supplies on-board power. These can be recharged in place or transferred to the surface for recharging in watertight containers. On-board gas supplies consist of high-pressure air, nitrox, and oxygen. Resupply of these gases can be conducted through a portable high-pressure line from the support vessel.