The Hollis Prism 2 (P2) Rebreather

Hollis Prism 2 Rebreather

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Rebreathers UK are proud to be the appointed distributor for the Hollis Prism 2, a fully closed circuit Rebreather, ideal for exploring open ocean, caves, or wrecks. This unit can be electronically or manually controlled which means you choose how you want the loop PPO2 maintained.

Includes option for front-mounted or back-mounted counterlung. Combined with the rear mounted radial scrubber, the Hollis Prism 2 provides easy breathing with low resistive effort and low hydrostatic loading. The Hollis 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. Tanks and valves are purchased separately.

Breathing Loop

Hollis Prism 2 Front Mounted Counterlungs

Front Mounted Counterlungs

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 actuator.

Hollis Prism 2 Back Mounted Counterlungs

Back Mounted Counterlungs

Back Mounted counterlung positions lungs behind the diver leaving the chest free for attachment of additional tanks and accessories. This also allows improved streamlining with less drag and better horizontal trim.

Features a 2 piece bag design for improved WOB performance and easy removal of the internal lung for cleaning or replacement. ADV Upstream Valve design is reliable and resistant to free flow which is a benefit for the addition of valuable diluent gas. All gas delivery systems on the Prism 2 have both automatic and manual function. Water Trapping T-pieces keep excess water from the breathing loop inside the counterlung for easy draining. Streamlined Hose Fittings keep LP hoses routed inside closest to the diver which avoids overhead interference. Machined DIL and O2 MAV controls ensure a rugged and reliable design, also allowing offboard gas plugin on both sides.

Hollis Prism 2 Radial Scrubber

Rear Mounted Radial Scrubber

The Hollis Prism 2 utilizes a user packed, radial 5.5lb CO2 scrubber, which features the best possible duration, insulation and work of breathing on the rebreather. The scrubber canister is mounted vertically on the backplate and between twin supply cylinders (one each, oxygen and diluent). The clear scrubber bucket is molded from Engineered Thermoplastic. This Hollis exclusive design ensures the CO2 scrubber is installed, packed and provides a visual for positive loop integrity.

Hollis Prism 2 DSV and BOV

High Performance DSV and BOV

Every Hollis Prism 2 ships complete with a DSV (Dive Surface Valve) standard and BOV (Bailout Valve) as an available option. The BOV features a high performance regulator valve, is incredibly lightweight and is a direct bolt on for your Prism 2 to replace the DSV. The Prism 2 BOV is considered a basic safety device for the rebreather by many professionals and meets the requirements for training in Technical rebreather courses


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.

Primary Display

Hollis Prism 2 Heads Up Display

Heads Up Display (HUD)

The Primary Display (HUD) consists of 3 bicolor (red/green) LEDs mounted on either the right or left side of the DSV/BOV mouthpiece just below eye level. Each LED provides a status indicator for its corresponding O2 sensor by using a “Smithers Code” flashing the status on a cycling 5-second loop during the dive.

Hollis Prism 2 Heads Up Display

Secondary Display

Hollis Prism 2 Computer


The Shearwater Petrel is the computer display on the Hollis Prism 2 and was chosen for this application as it is one of the most advanced mixed gas CCR computers available today. The Petrel is designed to control the Prism 2 setpoint and uses a basic decompression algorithm known as Buhlmann ZHL-16C which has been modified by the use of Gradient Factors.

Complete Customisation

Customize the Hollis Prism 2

A Full Range of Customisation Options

Ordering a Hollis Prism 2 has never been easier with the Rebreathers UK Prism 2 Builder option. Quickly add accessories such as our high performance BOV, tanks and valves, wing and harness type, all right from the factory.

Build Your Prism 2 Rebreather

Full Feature List

  • Choice of Front Mounted or Back Mounted Counterlungs.
  • Industry Best WOB – 1.57 J/L at 40 meters using AIR as diluent
  • Unit weight when fully charged, in standard configuration – approx. 19kg (With Steel Backplate)
  • Split counterlungs allows inhale and exhale counterlungs for high work loads.
  • Counterlung drains make it easy to remove water during a dive
  • All gas lines external to the breathing loop prevents leaks from affecting the PPO2
  • Automatic diluent addition valve adds diluent during descent or when the loop volume is low
  • Manual diluent addition valve adds on board or off board diluent for loop flushing
  • Gases – Air, Trimix, and Heliox
  • Manual oxygen addition valve allows for manually controlling oxygen PPO2
  • Integral harness and BC or Backplate standard makes the Prism 2 ready to dive out of the box
  • High performance open circuit Bail Out Valve option
  • Full range of wings/harness gives the ultimate customization
  • Accepts 13, 19, or 30 cu.ft. cylinders for flexible gas management
  • Eye level LED Primary display provides easy to monitor system status
  • Displays PPO2 for each oxygen sensor is used to control PPO2 manually & assure electronics system is nominal
  • External power switch is easy to power on
  • Easy calibration with a push button O2 calibration
  • Large OLED Secondary Display is easy to read, even for your buddy
  • PPO2 Monitoring of Three Sensors Continuous display of each sensor’s PPO2, mv reading easy to access
  • Closed Circuit & Open Circuit, 5 gases supports diluent switching & Multi-gas mix dive plans
  • 2 button push OC bailout – If you have to leave the loop, quickly switches to bailout support
  • CNS Tracking based on real time oxygen exposure
  • Software Update via web
  • Dive Log Download
  • Stainless Steel Stand Included


Length21 in (53.3 cm)
Width17 in (43.2 cm)
Depth9 in (22.9 cm)
WeightApprox. 47 lb with tanks
Scrubber Flow DesignRadial
CounterlungsFront Mount 3.5L / Back Mount 4.0L
PO2 Set PointsAdjustable (0.7, 1.0, 1.2, 1.3, 1.4)
O2 Sensors3 Galvanic
Sensor Life12 months in air or 100 hours dive time
Heads Up DisplayYes, 9V battery powered sequential LED
HandsetYes, (Shearwater Petrel) Powered by Lithium Cell
Battery Type9V Alkaline / 3.6v Lithium Cell
Battery Life40 Hours
Automatic Setpoint SwitchYes
Integrated Weight SystemYes (Optional)
Scrubber DurationEN 14143 testing rated the Prism 2 at 40m 4 Deg C (1.6L/min of Co2) at 190mins/3 hours 10mins on AIR Dil and 215mins/3 hours 35mins on Trimix
Hollis Prism 2 Rebreather