What is a CCR (Closed Circuit Rebreather)?

With OC (Open Circuit) diving gear the diver only uses a fraction of the oxygen supplied by the tanks. With each exhalation he releases gas and unused oxygen into the ambient atmosphere and its gone forever.

The basic working principle of a closed circuit rebreather consists of recycling the breathing mixture within a loop. To keep a constant ppO2, small amounts of oxygen gets injected (either manually or automatically) into the exhaled gas to replace the oxygen which got metabolized by the diver. Carbon dioxide produced by the diver gets absorbed by the Scrubber (absorbent). The composition of the breathing mixture changes continuously during the dive.

Benefits

Gas efficiency: As each breath you exhale gets recycled and enriched with oxygen so you can breathe it again, the amount of gas you actually have to carry with you gets drastically reduced. This comes in handy on trimix dives as helium tends to get more and more expensive. Keep in mind though that you should always carry adequate bailout with you on all dives to make it safely up to the surface in a worst-case scenario.

Reduced Decompression – extended no decompression times: On a CCR you are diving following a fixed partial pressure of O2 which means its fraction is changing with depth (exactly the opposite compared to OC dives). Therefore, you always are exposed to the lowest concentration of inert gas possible, regardless of depth, which leads to longer no decompression times and more efficient decompression profiles.

Warm gas: gas passing to a little opening in the first stage is expanding and cooling down till it reaches the OC diver. A CCR diver is breathing the same gas again and again and only little by little other gas is added which results in a more warm and moist gas so mostly you do not get as easily cold on a CCR.

Bubbleless silence! You will produce bubbles due to the expanding gas on ascents but in between you will have these moments of absolute silence seeming that the laws of physics are not applying to you! This is especially a huge advantage if you are into observing aquatic life!

Drawbacks

Costs: The units itself are still quite cost intense and you should not forget about other expends like annual services and replacement of the oxygen cells plus Sorb, Helium and especially training. They really start to pay back though on longer and deeper dives were you either couldn’t do them anymore on OC or you would waste a lot of helium.

Complex: although the working principle of a ccr is quite simple – CO2 out, O2 in – don’t forget that we mess around with one of the most important things for us: the gas we breath! With a higher level of complexity, it is also important to gain and maintain good working principles with the unit (pre-dive preparation and maintenance) and by training essential skills.

No more controlling your buoyancy by breath: for most OC divers its already so second to nature that they don’t even realize on how much they depend on it till they do their first CCR dive. Your breathing pattern has no overall influence on your buoyancy as you only move gas from your lungs to the counterlungs forwards and backwards, but the volume actually never leaves the contact to your body.

Travelling: travelling with a CCR means an extra bag which you have to take into your accounts your planning your trip. Not all dive centers are rebreather friendly dive centers so you better check if there is Sorb available and if they have or at least can fill your CCR tanks. Do you can get spare parts or is it maybe better to bring your own spare kit?

Risk: With more complex machines also, more risks arise in the picture which we don’t even knew from OC diving. CCR diving is a commitment and a high level of self-discipline is a must! If you are not willing to learn and train you will bring yourself and buddy sooner or later into big troubles!



At Dahab Divers Technical we offer training on two different units:

X-CCR from iQsub

X-CCR powered by Shearwater is an expedition grade rebreather developed using years of experience with CCRs with respect to the needs of divers and explorers. The X-CCR has a compact and ergonomically designed hardware and facilitates easy tool-less assembly and maintenance.

Main features:

  • Durable and user-friendly design
  • Variable device connections
  • Expandable & upgradable
  • Variable configuration
  • Integrated HP & CO2 sensors
  • Reliable & simple

Prism2 from Hollis

The PRISM 2 is a digitally controlled electronic closed circuit rebreather with split Front-Mounted Counterlungs (FMCL) or Back-Mounted Counterlungs (BMCL). It incorporates a radial design scrubber for the best possible duration and work-of-breathing. All gas delivery systems on the PRISM 2 have both automatic and manual function. The Prism2 uses the Shearwater electronics.



Training

Dahab Divers Technical offers CCR training via IANTD. Your adventure starts with what commonly speaking is known as the

“MOD 1”

CCR Advanced EANx Diver

The course consists of min. one confined water session and six open water dives with a total of 500 minutes in water training using the specific Rebreather on which they are being trained.

Purpose:

This Program is designed to train competent divers in the safer use and technology of CCR for dives requiring decompression.

It is also especially useful to train divers who wish to dive up to 40msw as part of the Advanced EANx course if using air as diluent.

Prerequisites:

  1. Certifications requirements:
    1. Must be qualified in IANTD EANx Diver or equivalent.
    2. Must be qualified in IANTD Deep Diver or RCCR Deep Diver or equivalent.
  2. Age requirement:
    1. Must be a minimum of 18 years of age.
  3. Dive experience:
    1. Proof of a minimum of 50 logged dives.

CCR Advanced Recreational Trimix Diver and CCR ART plus

The course consists of min. one confined water session and six open water dives with a total of 500 minutes in water training using the specific Rebreather on which they are being trained.

Purpose:

This Program is designed to train competent divers in the safer use and technology of CCR for dives requiring decompression.

It is also especially useful to train divers who wish to dive up to 45 msw as part of the Advanced

Recreational Trimix course in which case the END will not exceed 30 msw when using Trimix as diluent

Prerequisites:

  1. Certifications requirements:
    1. Must be qualified in IANTD EANx Diver or equivalent.
    2. Must be qualified in IANTD Deep Diver or RCCR Deep Diver or equivalent.
  2. Age requirement:
    1. Must be a minimum of 18 years of age.
  3. Dive experience:
    1. Proof of a minimum of 50 logged dives.

Extra Limits for CCR Advanced Recreational Trimix Plus

  1. For CCR Advanced Recreational Trimix Plus Diver Program, no dives may be conducted to depths greater than 51 msw-
  2. Two (2) extra dives with a total run time of 60 minutes.
    1. At least 1 dive must be between 40 msw and 45 msw
    2. At least 1 dive must be between 42 msw and 51 msw


“MOD2“

CCR Normoxic Trimix Diver and CCR Normoxic Trimix Plus Diver

The course consists of min. one confined water session and five open water dives with a total of 360 minutes in water training using Air, EANx or Trimix.

Purpose:

This Program is designed to train divers in the safer use of Rebreathers for dives using normoxic helium-based gas mixtures.

The knowledge and skills taught in this program are designed to qualify divers to perform Normoxic Trimix Dives up to 60 msw or Normoxic Trimix Plus dives up to 70 msw.

Prerequisites:

  1. Certifications requirements:
    1. must be qualified in IANTD Advanced EANx or equivalent
  2. Age requirement:
    1. Must be a minimum 18 years of age.
  3. Dive experience:
    1. Must provide proof of a minimum of 100 logged dives of which at least 25 rebreather dives and 50 hours on the unit with at least 50% of them logged on the same CCR to be used in the course.
    2. At least 30 dives were deeper than 27 msw.

Extra Limits for Rebreather Normoxic Trimix Plus:

  1. For Rebreather Normoxic Trimix Plus Diver Program, no dives may be conducted to depths greater 70 msw.
  2. Oxygen partial pressure may not exceed:
    1. On dives with a maximum depth of 60 msw the Diluent PO2 must be no higher than 1.1 ata during the working portion of the dives;
    2. On dives below 60 msw the Diluent PO2 must be no higher than 1.12 ata during the working portion of the dives and may not have an END greater than 39 msw
  3. Decompression gases:
    1. The use of 2 DECO gases are mandatory for all dives
    2. During the class student must demonstrate proficiency in using 2 DECO gases
  4. At least one (1) dive must be done be between 63 msw and 70 msw with a total run time of 55 minutes or more.
  5. Normoxic Trimix to Normoxic Trimix Plus crossover:
    1. One (1) Confined Water Session
    2. Two (2) Open Water Dives and 110 minutes of run time


“MOD 3”

CCR Trimix Diver

The course consists of min. one confined water session and five open water dives with a total of 360 minutes in water training using air, EANx, Trimix or Heliox provided the depths are acceptable for the gas used.

Purpose:

  1. This Program is designed for those individuals already involved in deep diving activities but is not intended to be used as an enticement to divers who are content to remain in Sport or EANx diving limits.

  2. Trimix affords a safer means for deep water exploration for divers who dive deep or perform with a clear head at depth. The IANTD Trimix Diver Program requires the diver to be self-sufficient/reliant.

The knowledge and skills taught in this program are more than adequate to qualify divers to perform Trimix Dives outside of training up to 100 msw.

Prerequisites:

  1. Certifications requirements:
    1. Must be qualified as an IANTD Normoxic Rebreather Diver or equivalent.
    2. Must be taking the Normoxic Rebreather Diver and Rebreather Trimix Diver course on an approved Rebreather for mixed gas diving, with all dives other than confined water made on Trimix or Heliox.
  2. Age requirement:
    1. Must be minimum 18 years of age.
  3. Dive experience:
    1. Must provide proof of a minimum of 200 logged dives with at least 100 hours on the rebreather to be used.
    2. At least 25 dives were to depths between 40 msw and 60 msw.
    3. If already certified as Rebreather Normoxic Trimix Diver on another recognized unit by IANTD, 25 rebreather dives and 50 hours must be on the unit specific for the class.