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The 5 Arguments About Rebreathers I Hear From Non-Rebreather Divers: Part 2

The 5 Arguments About Rebreathers I Hear From Non-Rebreather Divers: Part 2

Welcome back, if you're just reading for the first time, this is the continuation of our article from last week.

In Part 1 we addressed the two arguments...

  • I've been doing these dives on open circuit for years

  • It's too much work

In Part 2 I’ll address the final three:

  • Too complicated

  • They're dangerous

  • It's too expensive

“Rebreathers are too complicated”

If you’re an adult living in a developed country chances are you’ve driven a car. You get in the car, you turn the key, and you go. Once in a while you’ll bring the car in for service. If you’re like most people driving a car you don’t do this yourself.

You probably don’t know the intricacies of valve timing, engine compression ratios, brake pad engineering, tire rubber chemical composition and tread layout, electronic control unit programming or how to do a myriad of repairs that are possible.

Capt Andy Favata diving his rebreather on the U-853

You are a user. You are not a technician or engineer.

Now lets look at rebreathers. Yes, it’s true, rebreathers have more pieces than their open circuit counterparts. But what does this mean to a user? Does this make it too complicated for a layperson that doesn’t have an engineering degree from MIT? Not even close.

A rebreather diver has to build and break down their units on a regular basis. They are not engineers or inventors. They are, for lack of a better phrase, simply following instructions. Thankfully modern rebreathers are built with the end user in mind. Simplicity in assembly is a major focus of rebreather design.

For example, I teach on and use a rEvo rebreather. For the purpose of our exercise lets look at our build up. Now for this example I’m deliberately skipping safety checks to illustrate a point, DISCLAIMER: DO NOT USE THIS AS A BUILD PROCESS! If you do please drive to your nearest rEvo Instructor and give them your rebreather. Proceeds of sale will go to the charity of your choice.

That said…

In normal build-ups we can break it down to 5 main installed pieces with four o-ring sealing surfaces for the breathing loop itself (6 if you include the two tanks)

Shammies, Scrubbers, Cover, Tanks, Loop Hose.

  • If you can roll up a hand towel, you already have the skill to put a shammy in the rebreather.

  • If you can place items in a shopping basket, you’ve got what it takes to install the scrubbers.

  • Have you ever closed a cookie tin? You may just be a scrubber cover engineer!

  • Know how to attach a regulator to a SCUBA tank? Lets hope so at this point.

  • Can you screw in a light bulb? Boom! You’re a savant at those hose attachments.

People who have never actually built a rebreather seem to have it in their heads that we’re assembling a jet engine but it’s just not the case. Now obviously there’s more to it throughout our build. I’ve skipped over a series of critical, but easy to perform, equipment safety checks designed to catch any problems. This brings us right into the next argument I hear (like how I did that there? I know I’m impressed also)…

“Rebreathers are too dangerous”

"17 As soon as they had brought them out, one of them said, “Flee for your lives! Don’t look back!”…26 But Lot’s wife looked back, and she became a pillar of salt." (Gen 19:17, 26)

Someone tells you to do something that is potentially life saving you should listen right? It couldn’t be any more cut and dry. Do it or something bad happens.

Glad we’re on the same page here.

Without going into a 60-page dissertation about psychology, statistics and possible scenarios it’s apparent that the two major causes of diver accidents are medical events and/or human error. As an instructor we can’t control unforeseen medical issues. All we can say is live a healthy lifestyle and get checked out by your Doctor. Either way it's not specific to diving a rebreather.

What I can attempt to control, through proper training, is human error.

Human error involving rebreathers falls into two main categories:

1. Error in use

2. Error outside use (assembly, inspection and maintenance)

We make it abundantly clear during training that if you cannot follow the simple, but crucial, directions we teach you (don’t look back or you’ll turn into a pillar of salt!) you’re going to have a bad day at some point.

It’s all a matter of religiously sticking to the procedures taught.

Over the years manufacturers have made rebreathers more and more ‘human proof’, things such as inability to install parts wrong or switched, check lists and electronic warning systems, to name a few, have become commonplace. I’m happy to say instruction and procedure has been refined as well.

Throughout training new rebreather divers practice in-water drills over and over in order to turn procedure into reflex. We then encourage students to continue to practice skills after training as well.

Unfortunately, like all things in life, we often have a level of contentment with our abilities which develops over time. This can lead to complacency. Rebreather divers are taught that this is our biggest enemy. Follow and practice everything you’re taught and I’d argue that any increased risk on a rebreather is negligible compared to open circuit.

I should also mention that I personally feel safer performing technical dives on a rebreather than using open circuit and know many world-class divers who feel the same. For me it’s a matter of options.

The failures of Open Circuit diving equipment are generally absolute and leave you with no or reduced breathing gas supply.

Rebreathers, on the other hand, can give the diver the ability to ‘limp out’ of failures using less efficient operation modes. These failure modes may still be more efficient than pure open circuit bailout.

For example, a rebreather diver loses their oxygen bottle and all their electronics (man you’re having a fun day). They still have, in their back pocket, the ability to use their rebreather as a gas extender by manually operating it as a “semi-closed” rebreather (we learn how to do this in training). A method that may be able to extend open circuit gas upwards of 8 times (more or less dependant upon depth) what breathing from a normal regulator would be.

My personal favorite advantage is the time benefit a diver on closed circuit gains. Let’s say you’re lost in a cave or wreck, would you rather be on a set of open circuit doubles with limited gas or on a rebreather with hours of time?

There is also the perception with non-rebreather divers that you can be swimming along on your rebreather and suddenly without warning you black out. It’s a valid concern if you don’t have any idea how they work or operate.

Loss of consciousness can happen from a few things on a rebreather. Oxygen levels being too high or too low are the ones that come to mind first. Levels too high can generally be fixed easily by adding diluent gas into the rebreather manually to bring levels back to normal. The concern of runaway oxygen addition is also present, and is just one more thing we train for and practice responding to. I can tell you, however that if this happens you would certainly be able to respond accordingly after training.

The concern over low oxygen levels is equally important. In training we have a drill that shows a diver just how long it takes oxygen levels to decrease on a rebreather even when fresh oxygen isn’t added. We turn off our oxygen cylinders and monitor our computers for a preplanned small drop. Every person who does this comments that they were surprised just how long it takes. You would have to be totally ignoring your O2 levels for long periods of time to allow it to happen. It’s the really open circuit equivalent of never checking a pressure gauge. Unless you have jedi training and can sense what’s going on then this is probably a bad idea (I think Shearwater Research is working on it for the next software update though).

The other big cause for concern on a rebreather is CO2. Excessive CO2 levels would generally be caused by two things, CO2 Scrubber problems or one-way check valve issues.

Scrubber issues usually fall under:

  • Incorrect procedure in packing the scrubber

  • Incorrect procedure in storing absorbent

  • Using the scrubber for too long

  • Flooding

Scrubber packing is an easy process, however, if you aren’t trained properly or stop using the correct procedure you could have an issue. Again, this is avoidable.

Similarly, follow the procedures in storing absorbent. Keep it sealed in its container, don’t use it past the expiration date, don’t put it in extreme temperatures or crush it. Pretty simple there too.

Overusing a scrubber is also a big no no that’s easily avoidable. Every rebreather manufacturer tests their rebreather for what they consider is a safe maximum amount of time to use the absorbent on a dive. Stay within it.

Flooding is the final potential issue. Before our dives we vacuum check our rebreathers for leaks. It’s easier than it sounds and its benefits cannot be overstated. When water gets into a rebreather (whether it be from incorrect assembly or use) it generally stops it from functioning as a rebreather. Again, a situation that we train for and work to prevent in the first place.

The other concern is check valves. These valves ensure that exhaled and inhaled gas move in the correct directions. This functionality is easily checked prior to assembly and the procedure is taught in class as well.

Seeing a common thread here? Issues are avoidable and manageable if you just do the simple things you learn and practice them regularly.

“Rebreathers are too expensive”

There’s a saying that goes, “If something should ever happen to me, don’t let my spouse sell my SCUBA gear for what I told them I paid for it.”

Ok, I’ve put this one last because I’m hoping nobody will read it. Still here? Dang. All right I’ll admit it. Rebreathers can be expensive.

A typical Closed Circuit Rebreather can run you anywhere from $5k or so used to the $11k range with training. Also proper training with a professional can be a decent time investment as well.

However, there’s a great incentive program when you buy a rebreather…

"Buy a rebreather and save up to 90% on trimix fills for life!"

With helium prices at all time highs, filling a set of double cylinders can be well over $100 for a single dive. Not including whatever decompression or stage gasses you’ll be using as well.

Weigh that against filling a small 2 or 3L rebreather cylinder and over time you start to recoup some of your initial investment.

Honestly though, this is one thing I can’t help you with. All I can say it that they’re worth it. So get out there, sell your stamps, donate body parts, do what you have to do people.

I’ll throw this in also. You’ve read all the above and you’ve decided it’s time to buy a rebreather. There are some new things to think about.

Like everything, you have to decide what you’d like through research. Look into everything about them. Become an expert as best you can. Call an instructor, call multiple instructors for different units, and harass multiple current non-instructor users who have nothing to gain or lose by speaking openly.

One thing I try to do with potential students is to tell them which questions they need to be asking and to not just trust me but to verify what I say elsewhere. I encourage people to not just buy what the hot unit is that your local shop is trying to push but to really look around. A rebreather is a major purchase for most, do the research. Not only will it help you make a better choice but when you do pick one you’ll go into training knowing more and that you made the right decision.

So there it is, the 5 arguments against rebreathers. Whether you’re just starting out or have been diving open circuit since the original Aqualung, I’m hoping you’re now armed with just enough to get you started on forming an educated opinion regarding rebreathers.

Thanks for reading and stay tuned for our future articles. If there’s a topic you’re interested in let us know! Should you have any questions about rebreathers or how to get started I’m always here.

Live Here. Dive Here.

Capt Tom McCarthy

rEvo Instructor

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