It’s breathing loop which is a keyed one way assembly consists of a closable mouthpiece assembly with mushroom check valves either side, which ensure uni-directional flow.


A radial flow scrubber canister is mounted vertically on a backplate attached to the integrated BC, between twin supply cylinders (one each, oxygen and diluent).


Dual, front mounted counter lungs provide the diver with a flexible reservoir equivalent to the maximum displacement of the diver’s own lung volume and ensures the lowest possible hydrostatic loading. These counter lungs are fitted with both automatic and manual gas addition systems and a variable volume control valve (used upon ascent to vent excess expanding gas volume or to purge the loop). Diluent addition is automatically achieved as hydrostatic pressure increases and the counter lung collapses against the valve actuator.


The electronics, sensors and batteries are mounted in the electronics head assembly at the top of the scrubber, with supply hoses feeding over the diver’s shoulders into the top of the counter lungs. An analog LED primary display offers a quick reference of unit performance with status and alarm indicators while an independent digital OLED secondary display verifies the unit’s performance.


With the electronics switched on, the secondary also provides a status check for the battery and displays the set point selected for the dive along with other critical information. The electronics vote between the three proprietary galvanic sensors and control the operation of a low wattage solenoid valve on the oxygen supply.

Rebreather Quality Assurance

  • 100% In-House Assembly – Every Prism 2 is hand assembled and tested in Salt Lake City, Utah, including a pressure test to 300’ prior to shipment
  • Module C2 Certificate from SGS – Hollis Rebreathers systems and processes are audited annually to ensure compliance to regulatory requirements. This ensures our products consistency exceed industry standards.
  • Critical oxygen components certified to ASTM G93 Level B and requirements of MIL-STD-1330

Prism 2 CE Certification

The Prism 2 Rebreather is CE approved for sale and training in the UK and EU marketplace. Both the front mounted counterlung and back mounted counterlung variants far exceed all test requirements and are in accordance with the EN 14143:2013 standard.