Hollis Prism 2


The Prism 2 is a fully closed circuit Rebreather, ideal for exploring open ocean, cave, or wrecks. This unit can be electronically or manually controlled which means you choose how you want the loop PPO2 maintained.

Includes shoulder mounted counter lungs and rear mounted radial scrubber which provide easy breathing with low resistive effort and low hydrostatic loading. The Prism 2 has also been tested by ANSTI at 100M and has the lowest WOB of any mixed gas CCR on the market at 0.94 J/L.

The standard kit includes an electronic secondary control and primary LED displays with a backplate/wing assembly that provides a complete kit ready to dive out of the box. Unit can also be purchased with or without tanks/valves.

SKU: 240.6520.000 Category:


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

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.

Independent 3rd party testing has also rated the Prism 2 the lowest work of breathing of any mixed gas rebreather available today at 0.94J/L. Click here for actual test reports: ANSTI_Prism2WOB_review.pdf

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).


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 ensures the lowest possible hydrostatic loading.

These counterlungs 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

Length 21in (53.3 cm)
Width 17 in (43.2 cm)
Depth 9 in (22.9 cm)
Buoyancy neutral
weight approx. 47 lbs (fully charged) with 19 cuft tanks
Scrubber Flow Design Radial
alternate inflator bail out yes (Hollis 310)
counter lungs Over the shoulder
PO2 set points adjustable (0.7, 1.0, 1.2, 1.3, 1.4)
O2 sensors 3 galvanic
Sensor life 12 months in air or 100 hours dive time
Heads Down Display Yes, battery powered sequential LED
Analog PO2 display (Secondary) Yes, powered by O 2 sensors
battery type 9 volt
battery life 40 hrs
automatic setpoint switch Yes @ 20 ft (6.1m) on Descending, 18 ft (5.5 m) on ascent
integrated weight system yes
Diluent bottle sizes compatible 13’s, 19’s; 30’s (cuft)

1.9, 2.7; 4.4(liters)

O2 bottle sizes compatible 13’s, 19’s; 30’s(cuft)

1.9, 2.7; 4.4(liters)

scrubber duration 245 min @(60 fsw, 40F, 1.3L/min CO 2,0.5%CO 2 SEV)

Additional information

Weight N/A
Dimensions N/A



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