Hollis Prism 2 Rebreather
Technically Focused
The PRISM 2 is an electronically or manually controlled, constant PO2, modular, closed circuit diving system.
As open circuit (SCUBA) divers, we rely upon filling our lungs with air from a pressurized gas tank with every inhalation and then exhausting that volume of air into the surrounding water with every exhalation. As we descend deeper, the water pressure around us increases, and the volume required to fill our lungs increases; in other words, our air supply depletes more quickly the deeper we dive.
A rebreather recycles rather than vents the exhaled breath. The exhaled breath passes into a closed loop, where it is pushed through a chemical absorbent (scrubber) to remove the carbon dioxide and returns through the other side of the loop for the diver to re-breathe, hence the name “closed circuit rebreather” or CCR.
Breathing Loop
Its breathing loop, which is a keyed one-way assembly, consists of a closable mouthpiece assembly with mushroom/check valves on either side, ensuring uni-directional flow.
Independent 3rd party testing has also rated the Prism 2 the lowest work of breathing of any mixed gas rebreather available today.
Status Check
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.
Scrubber Design
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).
Electronics
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 counterlungs. 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.
Counter Lungs
Dual, front-mounted counterlungs provide the diver with a flexible reservoir equivalent to the maximum displacement of the diver’s own lung volume and ensure the lowest possible hydrostatic loading.
