New to Rebreathers or CCR

CCR Advantages

Dive for longer

Use less gas

Because a CCR ( Closed Circuit Rebreather ) recirculates the gas we breath we can use a lot more of the oxygen and waste less gas. A single oxygen 3ltr cylinder can often give us 3-5 hours of diving. The main effect is how much oxygen we metabolise. Typically this is about 1 litre of oxygen per minute. Depth makes little diference we use the same at 10m as we do at 100m! Very different to normal scuba.

Longer No stop decompression dives

A CCR mixes the gas as you go so that you are always breathing the optimum mix of Nitrox or Trimix.

Shorter Deco

If you do go into Deco then you off gas faster due to breathing the opimum mix. This gives you much shorter Deco.

Bubble Free and Silent

A CCR produces very few bubbles making is super silent so you can get up close and personal with marine life making it a great choice for photography.

Warmer - More comfortable

We are breathing warm moist air instead of cold dry air. This keeps us warmer in cold conditions and we do not get dehydrated like normal scuba. This makes us a lot less tired.


The Hollis Prism 2 CCR is so versatile from Shallow 10m dives to 100m deep dives, fill your gas, pack your scrubber and away you go (within your certification limits). From open water drift dives to extended Cave, and deep Wreck exploration dives the Prism 2 is ready to go.

CCR Cool factor

The Hollis Prism 2 and some other CCRs are just plain COOL !

How does a CCR or Rebreather work?

This is a simple guide to how a CCR or Closed Circuit Rebreather works, often just called a rebreather.

The CCR is very simple in principle. When we breathe out on normal Scuba the gas is vented into the water and lost making a lot of noise. We can only use a very small amount of the oxygen in that gas, the rest is wasted.

A CCR recirculates this wasted gas removing the Co2 we generated so that we can breath it again and use more of the oxygen, a lot more.

A rebreather captures this vented gas in a counter lung (bag) and then passes it through a scrubber to remove or scrub out the Co2 and then we breathe it again. We will have metabolised some of the oxygen so every now and then we need to add oxygen.

A electronic CRR like the Hollis Prism 2 also controls the amount of oxygen as we go up and down to change the Nitrox or Trimix gas that we are breathing to make it the safe opitmal gas for that depth.

Most modern electronic CCRs do this by measuring the breathing loop (Gas that we are breathing) and injecting Oxygen or DIL (diluent - normally Air of Trimix) as required to keep the mix optimal for the depth we are at.


CCR Rebreather Training - What it takes

There are lots of Agencies that can train you to use the Hollis Prism2 CCR and other rebreathers. This is a basic review of what is normally involved and how long it takes.

There are 3 basic levels

MOD 1 or CCR40

This is the first level, some agencies only teach "no Deco" on their first level courses while others include Deco such as PADI. This normally qualifies you to 30 or 40m with limited Deco using air diluent (DIL). Those agencies that do not include Deco in the first level have an additional course (additional cost?) to add limited deco. So you need to check what is included in the basic MOD 1 user course you are considering. It might be cheaper only because you get less training for your money. Courses normally take about 5 Days if you are new to CCR diving.

MOD 2 or CCR60

This second level builds on the first 40m Air dill certification and qualifies you for 60m unlimited deco using none hypoxic Trimix diluent. With CCRs generally you want Trimix below 40m unlike 50m on open circuit TEC dives, this is due to the effect of the scrubber and gas density at depth.

MOD 3 or CCR100

This last level builds even more on MOD 2. 100m is a low way down so it is not for everyone. You need a lot of experience of diving your CCR before even thinking about 100m dives. This qualifies you to 100m dives using hypoxic diluent (Dil with less than 16% oxygen).

How long does CCR training take?

Each of these courses / modules take about 5 Days with your instructor plus the home or online study normally required. You will cover both generic CCR theory that covers all CCR types and specific theory for your chosen CCR. Normally there are 6 to 8 dives depending on your chosen agency on your CCR and you must reach the standard required at that level to dive safety. There is also an exam or 2.

Training is normally unit specific so when you change to a new make of CCR you need to do a shorter course that just deals with the differences between your current CCR and the new CCR. These qualifiers or additional unit courses normally take about 2 days each.

You want to choose your instructor with care, there is a lot to learn and it is not about how fast or how cheap you can do it. You want good quality training that will keep you safe and help you get the most from your CCR. Remember you pay for instruction, you earn your qualification!

Find out more about Hollis Prism 2 Training

Hollis Prism 2 - Training calender

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