Choosing a Rebreather
You want a rebreather but – which one? There are dozens of closed-circuit rebreathers available and they all claim to be the best. Is there one that’s better than the other? How do you pick the right unit?
What is the best rebreather?
There is no single best rebreather. That does not mean they’re all on the same playing field though. There are design elements that are better than others. Some compromises make some units worse at one thing, but better for a specific dive in a specific environment. Rebreathers are expensive. Buyers want to feel happy about their purchase so they hide behind phrases like “bulletproof design” instead of analyzing one unit’s compromises over another. When choosing your rebreather, you must consider various factors and make designs based on objective metrics.
Important considerations
Diving goals
The first question is where do we want to go in a reasonable timeframe? Reasonable timeframe is a key concept here. If you want to do 500ft dual CCR cave dives then it doesn’t matter which unit you start with. You have years and hundreds of hours of CCR diving to complete before getting to that level and will most likely use many different units for different purposes. What is your goal within the next few years on CCR? Is it deep shipwrecks, photography, or longer penetration cave dives? Establishing a dream dive gives us a realistic purpose and goal for our CCR journey. If our local caves require sump techniques we should look at a more compact unit. If we travel exclusively for diving that presents another form of consideration. There will always be outliers but where will we use it the most and where do we want to go in the next few years?
Configuration styles
The basic configuration platforms we can utilize are: Backmount, Sidemount, Split Can, and Chestmount. Each offers unique opportunities.
Backmount – traditional backmount CCRs offer the most robust abilities. There are options for long CO2 capacities, superior water tolerance, and a simple but standardized bailout configuration.
Sidemount CCRs are very mission-specific units for environments that have difficult entries or small passages. In general, sidemount CCRs aren’t ideal for beginner divers. The compromises they take to streamline the unit are appropriate for their users but typically don’t pay off for most CCR diving. Sidemount CCRs also reduce our core ability for sidemount redundancy because the unit sits where one of our cylinders would go.
Split can CCRs are designed to integrate into an existing sidemount system and allow cylinder redundancy. Like their sidemount cousins, they have design compromises compared to backmount units which make them less ideal for novice CCR divers. Water tolerance, work of breathing, and ease of rigging are examples.
Chestmount CCRs offer unsurpassed versatility for divers to integrate a CCR into their existing core platform. Chestmount CCR are the most versatile but still lack some design element benefits inherent to backmount CCRs. Counterlung volume, variety of inputs, and water tolerance are examples of these concessions.
Instructor base
A less popular unit with a good instructor might be better than the opposite, which is why factoring in instructor options is an important component of choosing your CCR. The most important question is “Does this person I’m paying to teach me how to dive this machine dive for fun in environments similar to where I want to go?’. If not, they may lack the relevance to your journey. Be wary of cheap instructors. A fair price is better than cheap. Never do training with instructors who guarantee course completion – that’s a red flag. There is nothing wrong with shopping around for instructors – even on pricing – but put your training goals first. If a CCR seems great but few instructors near you teach on it, then plan to travel for your course.
Support
It will break. It will need regular service. When it comes to service, longevity is more important than locality. If a great manufacturer is located out of the country then it still may be a good option. Rebreathers built in a garage by some guy – no matter how smart that guy is – will have less longevity of support than a rebreather made by a reputable company.
Human-friendly design
CCRs are designed to keep you alive and (as a side effect) enjoying your time underwater. There is a phrase commonly thrown around “Think of your rebreather as always trying to kill you”. That is a dumb phrase. The rebreather is designed to keep you alive. The environment, by nature of pressure and its effects on gases, is the attempted murderer. There are often compromises in design. For example, 3-pin Molex connector cells are not the best option. Many CCRs use these cells though. While the connection is finicky and annoying, they’re widely available and less expensive. Other style cells are often out of stock. While I don’t like molex cells I’m comfortable using them because they’re easy to get and swap between many units and analyzers. That’s an acceptable compromise that doesn’t affect safety.
Examples of human-friendly design
- Machining that prevents parts from being installed incorrectly.
- Few or no “parts of fatal omission” – small or easy-to-lose components that will cause catastrophic failure if forgotten.
- Assembly and disassembly use no tools and take a short time.
- Buttons/interfaces have location and tactile differences to determine it’s the desired input
Common fallacies
All rebreathers suit a purpose and there is no good vs. bad.
All rebreathers are designed with the same idea in mind “support life underwater”. There are no units out there designed to hurt, harm, or kill you. With that in mind, there are elements of design that make some components objectively better than others. This can be extrapolated to mean some similar units are better than their counterparts.
You should dive what others around you dive.
Being part of a community is awesome. Understanding your dive buddy’s configuration(s) is also awesome. Diving 20-year-old technology that has a higher chance of failure than a more modern unit is silly. If they all jumped off a bridge, you wouldn’t. I’ve seen this happen many times where a diver makes their purchasing decision based on “everyone is diving XYZ so that’s what I’ll get” only to have that community shift to something new and shiny after a year – leaving their primary purchasing decision invalid.
Rebreathers are safer because you have open circuit as backup.
Rebreathers have a significantly higher risk than open circuit. Your chances of hypoxia at the surface before a dive (the most common fatality) are very low on an open circuit second stage with analyzed gas. Those chances are not negligible on a CCR. The same applies to hyperoxia, hypercapnia, and probably cardiac events. While rebreathers offer more problem-solving time underwater and there are situations where rebreathers have saved lives that does not make them a safer platform overall. A 10ft deep reef is more suitable for snorkeling, just as some sites are more suitable for opencircuit, and others for CCR. Rebreathers should be purchased and used for dives where open circuit is logistically unfeasible. Any instructor who is using sales phrases like “no bubbles”, “warm gas”, and “safer” is doing you a disservice.
Demo as many units as possible before buying one.
People who take discover scuba experiences rarely decide to complete the full scuba certification. One part of this failure to convert is saturated and overworked instructors, the other is the overwhelming novelty of the experience. CCR demos for people who are not CCR trained are a half measure and often promote false positives or false negatives. Your understanding of the system is not mature enough to make a decision based on a short excursion. Most people hate CCRs after a demo dive. In your first CCR course you’ll spend hours in the classroom learning concepts, and hours assembling the unit. Those hours give you confidence for your first underwater dive. CCR demos lack those components and are typically a disservice to the diver. If you’re a certified CCR diver looking at other units I think demos are awesome.
An explorer uses this unit, which makes it good.
Exploration-level divers use rebreathers that suit their needs. The units they use may be mission-specific to them but less ideal for the diving you’re doing. Just because an explorer or influencer utilizes a piece of kit or methodology doesn’t make it universally superior. With this said, the requirements that exploration and expedition-level dives can give us good insight into the durability and reliability of a unit.
Takeaways
- Start with your goals, and establish needs based on those goals.
- Ask your prospective instructor about the benefits and drawbacks of the unit. Look for critical answers and explanations of why they’re comfortable with the compromises this unit has against another.
- Be wary of common fallacies and sales pitches.
- Dive your unit and enjoy it. Once you make a decision get on the unit and have a good time!
What unit do I use and why?
I dive and teach the Dive Rite O2ptima CM (choptima). It’s a chestmount electronic CCR. I chose it because it’s small, lightweight, has adequate scrubber duration, and great support from a reputable manufacturer. It isn’t perfect, but I’m very pleased with it and it suits my needs. Would a backmount CCR be easier to get into on a boat compared to putting on doubles+a chestmount CCR? Of course it would be, but then I lose a convenient bailout location (my backmount doubles) and the ease of travel. There are other benefits to the unit, I’m being purposefully short because this isn’t meant to promote my unit, but provide tips on choosing your unit. For more info on what I think about the choptima, check out my review.