Best CCR in 2025-2030 Rebreather Markets
- Thread starter Mas.
- Start date
Please register or login
Welcome to ScubaBoard, the world's largest scuba diving community. Registration is not required to read the forums, but we encourage you to join. Joining has its benefits and enables you to participate in the discussions.
Benefits of registering include
- Ability to post and comment on topics and discussions.
- A Free photo gallery to share your dive photos with the world.
- You can make this box go away
The Mares (Revo) Horizon SCR isn’t a great seller. It works but it’s too specialised (exactly the same as the Hollis Stormtrooper and the RB80 for that matter)
Chris-Wood
Registered
- Messages
- 13,621
- Reaction score
- 10,340
- Location
- Port Orchard, Washington State
- # of dives
- 1000 - 2499
The Horizon. It still exists sorta, hard to tell the extent old stock is still being sold vs actually made in 2025. Either way it's been a complete market failure.
Semi-Closed Circuit Rebreathers (SCR) vs Closed Circuit Rebreathers (CCR)
For the benefit of non-rebreather divers, an quick overview of the differences.
The human body consumes—metabolises—oxygen, converting oxygen into carbon dioxide in the exhaled breath (which plants consume, and produce oxygen).
All rebreathers are just a bag that you breathe in and out of. Fine for a few breaths, then you pass out through carbon dioxide buildup and lack of oxygen. Carbon dioxide is relatively easy to get rid of by breathing through a sodalime scrubber which filters out carbon dioxide.
The big issue is oxygen. Too little oxygen (hypoxia) and you quickly pass out, then drown. The human body can only withstand a limited pressure of oxygen: pure oxygen down to 6m/20ft; deeper than that requires the breathing gas to be diluted with nitrogen or helium. Too much oxygen (hyperoxia) and you may have a fit, then drown.
Modern rebreathers—that is every rebreather sold in the recreational world which we’re talking about here—all monitor oxygen levels.
Historical aside: there used to be “oxygen rebreathers” which would use pure oxygen. The depth limit was about 10m/33ft but the divers would have been selected for their oxygen tolerance (and were all fit young men). Lots of Historical Diving Societies around the world who love playing with that kit; off topic here, as are mechanical rebreathers.
A couple of definitions. The bag which is used to breathe in and out of is called the counterlungs. All airways including the breathing hoses, mouthpiece, scrubber, counterlungs are called the loop.
A closed-circuit rebreather will monitor the oxygen levels in the loop and add oxygen to the loop as required. This monitoring uses several oxygen cells—typically three cells, but often four or five—for redundancy as it is a safety-critical component and oxygen cells are like little batteries that expire within a year or two and are swapped out. Pure oxygen is added through an electro-mechanical solenoid valve in little squirts.
A CCR constantly mixes two gasses; pure oxygen and a diluent gas which is safe to breathe at the deepest depth planned, typically air or a trimix. The diluent is added during the descent as pressure increases. Once levelled out, diluent is no longer required (unless something untoward happens). A CCR only adds more oxygen to match the diver’s metabolic rate which is depth independent, normally around 0.6 litres of oxygen per minute—a 3 litre cylinder/tank contains 3 x 200 litres of gas = 600 litres, enough for many hours. The diluent cylinder/tank is similarly small, generally 3 litres. Both of those cylinders would be more than enough for several dives; they’re topped up more for prudence than need. As there’s very little gas used, diving with expensive helium isn’t a problem, costing a few bucks. (Example from my logs: 63m/210ft wreck dive with 45mins bottom time and 1h50 decompressing used 150 litres of oxygen and 120 litres of 13%oxygen + 51%helium = 60 litres of helium costing less than $6, the oxygen costing more than the helium!)
The issue with closed-circuit rebreathers is their technical complexity and skills required to dive the rebreather without dying. Tall tales like “I nearly died because I wasn’t monitoring my oxygen levels” are quite rare as the person passed out and drowned. Training and lots of practice is required, as is lots of preparation, packing scrubbers, cleaning, disinfecting, maintenance, following written checklists, etc.
There are a couple of an alternative type of rebreather called a semi-closed circuit rebreather. These do not use pure oxygen, but instead use a tank of oxygen enriched breathing gas (Nitrox) which is used to top up the oxygen levels in the loop. The good news is that you cannot add too much oxygen. However, you need to add considerably more gas to the loop and you still need to ensure the oxygen levels aren’t too low or you pass out and drown.
Semi-Closed Circuit Rebreathers (SCR) uses a lot more gas than a CCR as their only source of oxygen is through a dilute bottom-breathable gas such as 32% nitrox. This means that 3 times the gas is required for an SCR than a CCR which uses 100% oxygen. SCRs are frequently called gas extenders as they will extend the nitrox gas volumes by 5 times or more when compared with open circuit, breathing out bubbles. SCRs have a valve which will dump from the loop when more gas is added by the solenoid.
In essence a semi-closed rebreather has all the complexities of a CCR but without the flexibility. They’re also restricted to “recreational” diving, i.e. no decompression and max depth of 40m/132ft. A SCR is a little cheaper to purchase than a full CCR, but still have similar costs and maintenance as a CCR and are just as hard to dive.
CCRs offer a great deal of flexibility and when diving deep or long durations are massively cheaper to run than open circuit.
Bottom line: don’t bother with SCR, just go for a CCR.
I’ve only ever been on one boat where someone was diving the Hollis Stormtrooper recreational SCR. This boat was at the back end of nowhere (the very north-west of Scotland) and high-pressure oxygen was simply not available. The diver was a keen photographer and liked diving silent.
On every other boat I’ve dived upon CCRs dominate the equipment and for deeper wreck diving it’s rare to see someone on open circuit.
—
Edit: cleanup & rewording.
For the benefit of non-rebreather divers, an quick overview of the differences.
The human body consumes—metabolises—oxygen, converting oxygen into carbon dioxide in the exhaled breath (which plants consume, and produce oxygen).
All rebreathers are just a bag that you breathe in and out of. Fine for a few breaths, then you pass out through carbon dioxide buildup and lack of oxygen. Carbon dioxide is relatively easy to get rid of by breathing through a sodalime scrubber which filters out carbon dioxide.
The big issue is oxygen. Too little oxygen (hypoxia) and you quickly pass out, then drown. The human body can only withstand a limited pressure of oxygen: pure oxygen down to 6m/20ft; deeper than that requires the breathing gas to be diluted with nitrogen or helium. Too much oxygen (hyperoxia) and you may have a fit, then drown.
Modern rebreathers—that is every rebreather sold in the recreational world which we’re talking about here—all monitor oxygen levels.
Historical aside: there used to be “oxygen rebreathers” which would use pure oxygen. The depth limit was about 10m/33ft but the divers would have been selected for their oxygen tolerance (and were all fit young men). Lots of Historical Diving Societies around the world who love playing with that kit; off topic here, as are mechanical rebreathers.
A couple of definitions. The bag which is used to breathe in and out of is called the counterlungs. All airways including the breathing hoses, mouthpiece, scrubber, counterlungs are called the loop.
A closed-circuit rebreather will monitor the oxygen levels in the loop and add oxygen to the loop as required. This monitoring uses several oxygen cells—typically three cells, but often four or five—for redundancy as it is a safety-critical component and oxygen cells are like little batteries that expire within a year or two and are swapped out. Pure oxygen is added through an electro-mechanical solenoid valve in little squirts.
A CCR constantly mixes two gasses; pure oxygen and a diluent gas which is safe to breathe at the deepest depth planned, typically air or a trimix. The diluent is added during the descent as pressure increases. Once levelled out, diluent is no longer required (unless something untoward happens). A CCR only adds more oxygen to match the diver’s metabolic rate which is depth independent, normally around 0.6 litres of oxygen per minute—a 3 litre cylinder/tank contains 3 x 200 litres of gas = 600 litres, enough for many hours. The diluent cylinder/tank is similarly small, generally 3 litres. Both of those cylinders would be more than enough for several dives; they’re topped up more for prudence than need. As there’s very little gas used, diving with expensive helium isn’t a problem, costing a few bucks. (Example from my logs: 63m/210ft wreck dive with 45mins bottom time and 1h50 decompressing used 150 litres of oxygen and 120 litres of 13%oxygen + 51%helium = 60 litres of helium costing less than $6, the oxygen costing more than the helium!)
The issue with closed-circuit rebreathers is their technical complexity and skills required to dive the rebreather without dying. Tall tales like “I nearly died because I wasn’t monitoring my oxygen levels” are quite rare as the person passed out and drowned. Training and lots of practice is required, as is lots of preparation, packing scrubbers, cleaning, disinfecting, maintenance, following written checklists, etc.
There are a couple of an alternative type of rebreather called a semi-closed circuit rebreather. These do not use pure oxygen, but instead use a tank of oxygen enriched breathing gas (Nitrox) which is used to top up the oxygen levels in the loop. The good news is that you cannot add too much oxygen. However, you need to add considerably more gas to the loop and you still need to ensure the oxygen levels aren’t too low or you pass out and drown.
Semi-Closed Circuit Rebreathers (SCR) uses a lot more gas than a CCR as their only source of oxygen is through a dilute bottom-breathable gas such as 32% nitrox. This means that 3 times the gas is required for an SCR than a CCR which uses 100% oxygen. SCRs are frequently called gas extenders as they will extend the nitrox gas volumes by 5 times or more when compared with open circuit, breathing out bubbles. SCRs have a valve which will dump from the loop when more gas is added by the solenoid.
In essence a semi-closed rebreather has all the complexities of a CCR but without the flexibility. They’re also restricted to “recreational” diving, i.e. no decompression and max depth of 40m/132ft. A SCR is a little cheaper to purchase than a full CCR, but still have similar costs and maintenance as a CCR and are just as hard to dive.
CCRs offer a great deal of flexibility and when diving deep or long durations are massively cheaper to run than open circuit.
Bottom line: don’t bother with SCR, just go for a CCR.
I’ve only ever been on one boat where someone was diving the Hollis Stormtrooper recreational SCR. This boat was at the back end of nowhere (the very north-west of Scotland) and high-pressure oxygen was simply not available. The diver was a keen photographer and liked diving silent.
On every other boat I’ve dived upon CCRs dominate the equipment and for deeper wreck diving it’s rare to see someone on open circuit.
—
Edit: cleanup & rewording.
To add.. (the little I know about)
SCRs have a (more noticeable) sawtooth ppo2 profile (with higher variance) compared to CCRs
(Depending on the gas selection and depths)
There is also a tradeoff between efficiency (gas venting frequency/qty) and the stability of ppo2
A CCR can be used in an „scr mode“ sometimes when some issues arise mid dive (periodically flushing after some loss of a specific mix bottle); but that’s also a complex matter for users that went beyond my basic (mod1) training
I’m quite sure somone can restate my word salad in a much better phrasing
SCRs have a (more noticeable) sawtooth ppo2 profile (with higher variance) compared to CCRs
(Depending on the gas selection and depths)
There is also a tradeoff between efficiency (gas venting frequency/qty) and the stability of ppo2
A CCR can be used in an „scr mode“ sometimes when some issues arise mid dive (periodically flushing after some loss of a specific mix bottle); but that’s also a complex matter for users that went beyond my basic (mod1) training
I’m quite sure somone can restate my word salad in a much better phrasing
Not really. The SCRs are pretty inefficient and are really only for diving within recreational ranges — max 40m/132ft with no decompression (or very light deco). SCRs emit bubbles too.
The example of the out-of-the-way diver I gave would be diving around 10m/33ft to 25m/80ft — the Hollis SCR was being used as a range extender to enable nitrox using a small 5 litre tank for multiple dives a day over a week.
Photographers would be far better off with a CCR where there are no limits on depth and deco times and there’s no bubbles.
Most of the amazing underwater wildlife filming is done with CCR.
Personally, when blowing bubbles on OC, the fish swim away from you as they don’t like the bubbles. On CCR you have to swim through them as they’re just not bothered — literally batting them away so I can see the wreck!
Fat old english bloke
Contributor
Not just on boats, but hey, it’ll be ok.Reminds me of the bailout cylinder sizes that you see on British boats - maybe this is the secret.
Similar threads
