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Are You Prepared For Rebreathers?

A rebreather failure could go unnoticed.  When open circuit regulators fail, it's immediately obvious.  Either you get no air whenever you suck on the mouthpiece or (much more likely) you obtain a lot of and also a surprising rush of bubbles on your face.

Why You May Want To Think Twice

Needless to say, that a rebreather doesn't make you immune to DCS and nitrogen narcosis. Those risks remain, though the more sophisticated closed-circuit rebreathers can adapt your gas combination to reduce the DCS hazard.  The advantage of this rebreather's long term for most folks is you can make a few pitches on a single load of scrubber and cylinders.

Silence. Rebreathers exhaust few or no bubbles. That you do not hear that roar of exhaust bubbles, and do fish.  That allows one to get closer to marine living, and this explains the reason why rebreathers are very popular with professional photographers and some research workers.  You may not be rendered invisible, however, you appear to be alarming to most fish.

Atleast that is my guess after spending a lot of monthly studying and diving rebreathers.  It ends up that they will have some very real, valuable advantages over open-circuit, tank-and-regulator methods.  However, they possess some evenly real and serious pitfalls too.  When you possess some odd requirements and would be happy to make some sacrifices of the time and money, a rebreather may be godsend. However, most divers, for most purposes, will remain to prefer open circuit scuba for a long time in the future.

 Coupled with a rebreather does not give you that cotton-mouth feeling and doesn't chill you as muchbetter.

If a rebreather fails, the signs, if any, are somewhat more subtle.  You are still able to catch your breath as before since you are only passing the identical gas back and forth between your lungs and the breathing loop.  Even the CO2 content in that gas might be rising and the O2 content might be falling, but this won't be instantly apparent without signs, monitors and alerts. Rebreather diving is similar to flying on instruments, not by the"seat of your trousers."

Their stealth and extended bottom times have made rebreathers popular with technical and military divers for all decades.  Recently, lower prices and"userfriendly" designs have made rebreathers more appealing to recreational sailors just like you and me personally.  Really, several models are aimed specifically at the recreational sector.

Long dip times. The most important advantage of a rebreather is petrol efficacy.  Just one fill of a little petrol cylinder or cylinders as well as CO2 scrubber can last for anywhere from one to half an hour, based which rebreather it's. Unlike open circuit scuba, your gas duration on the rebreather is nearly independent of thickness, and that means you might, theoretically, spend all that time at the ground.

On the other hand, should you watch your devices and detect the issue promptly, you'll probably have more hours and energy to deal with it to a rebreather than you would on open circuit.  

Optimum gas mix.   They can continue to keep your own PPO2 constant regardless of thickness or exertion, or alter it on the fly for needs like de compression.  The advantage can be less nitrogen uptake and faster off-gassing --Put simply, more bottom time with less DCS risk.  Rebreathers are not created equal, however, and the less-expensive designs don't need this ability.

Is the possibility of diving?  Are traditional open circuit rigs bound for that oblivion of duck fins and two-hose regulators?  Are you ready to get rebreather diving?  Are rebreathers ready for you?

Even a rebreather failure could be deadly.  A rebreather is constantly mixing the gas in the breathing loop, removing carbon dioxide and adding oxygen.  Either component within the wrong percentage is noxious.  Much of the plan effort and a lot of the complexity of rebreathers goes into making that mixing function as accurate and reliable as possible. Nevertheless, it's not likely to get to the certainty of available circuit, where everything you breathe is simply what went in to the cylinder.  An open-circuit"bailout" jar and regulator is a good idea when Functional Safety in Diving  using conventional gear, however it's crucial with a rebreather.

The Very Initial Measures

Cost, weight, majority, advantage, etc..  These minor facets all weigh contrary to rebreathers.  Though the expense to buy one is scarcely minor, you are frequently told you'll save yourself money on every dip as you never need to refill tanks too frequently.  However, you do need to purchase scrubber compounds, and maintenance may be more expensive.  And can this 60 two-tank dive ship offer you a rebate unless you need to make use of its tanks?  Not likely.

Rebreathers, for example, bail out bottle, are often thicker and lighter than one tank and ruler, plus so they don't really fit well in to the tank-rack-and-bungee-cord gear channel standard on dip boats.  Airline traveling with tanks may be struggle and matches for oxygen and maybe even nitrox could be more difficult to locate, particularly in distant places.

Since you'll need to be coached by an instructor certified within your specific make and version, you might need to go to a different town and stay there for five weeks or for your own training class.

Here is what to anticipate, bearing in mind that every rebreather differs and requires a unique procedure.

Various rebreathers use marginally different sorts of CO2 absorbent and differing granule sizes, however it all looks much like kitty litter.

You will pour the absorbent in to the canister, then tapping on the canister sporadically to be certain the absorbent dissipates and thoroughly meets the canister.   You then'll seal and close the canister along with the simmer bottle or skillet.  Many anglers do that endeavor in home until the dip visit to minimize the clutter.  

Every Day on The Water

First is decided which rebreather to get.  Rebreathers differ significantly in not just price but capacities, the excellent split being if or not they truly have been closed circuit or semiclosed-circuit InDesign.

Closed circuit rebreathers have the best gas ingestion, the ideal mix control and, broadly speaking, the maximum capability, however, tend to be somewhat more complicated and costly. Semiclosed-circuit rebreathers are easy, robust and more affordable, with gas ingestion rates somewhere within closed circuit rebreathers along with open circuit scuba.

You could also think of such matters as depth and time limits, copies to restrain apparatus along with fail safe mechanics, guarantees, and just how many components have been completely being used and for the length of time, and much more.

Meanwhileyou will begin to construct a distinctive tool and spare parts kit.  You are probably going to need one or even maybe more spare oxygen tracks and assorted solenoids and detectors to your more complicated units. Additionally gas analyzers along with flowrate evaluation apparatus, based upon the machine.  Enhance this mouthpiecesbatteries, orings, tie wraps, silicone grease, etc..

More than open circuit, a rebreather dip starts before you will get wet and finishes once you are tender. Pre-dive and postdive look after that rebreather are crucial each time and can not be skipped.  Expect to devote an additional halfhour on every end of this dip.

Fill canister (s). Many semiclosed-circuit rebreathers make work with of one cylinder of nitrox.  You are going to need to decide beforehand that nitrox mix you'll utilize therefore that the skip valve orifice might be paired to it.  Most closed circuit rebreathers utilize two tanks, of oxygen and also a diluent (usually atmosphere, though other pollutants maybe options). Either way, but particularly if working with nitrox, you must analyze the gas your self to produce sure what exactly is from the canister.  If your bail-out system employs another cylinder, then you can require to refill this too.

Afterward there is training.   After that, just about any rebreather manufacturer will ask that you simply just consider a rebreather training class lasting 4 or 5 days.  The expense of the will probably be extra, normally at $500. Section of this program covers in-water skills such as how to translate resumes and tracks and also just how to change to backup systems.  The following part is trained in gathering and disassembly, servicing and upkeep of one's specific unit.

Pre-dive

Let us say you've believed the advantages and disadvantages and decided that you intend to dive using a rebreather.  What is the drill?

Build the rebreather.   Do not expect you'll build your rebreather between your dip briefing and the"pool open!"  C all.

Since you descend, upping pressure can fall the counterlungs as it drops BCs and dry matches.  

In to the water. Waddling round the deck at a rebreather was justly compared to carrying dual tanks, but once you are at the water the majority of the trouble stops.  A couple of differences to open circuit diving will hit you though.

Postdive

You'll have to become stingy when inflating your BC or draining your mask as gas employed for gas lost from the significantly smaller full source.  To precisely exactly the exact very same reason, you want to see your indicators carefully and you and your friend have to be attentive for air escapes.

One is you can not simply shed the mouthpiece in to the sport, because water will fill out the breathing loop and also the scrubber canister.  There's a valve to the mouthpiece you need to consider to close until you go from your own mouth.

Here, semi-closed - and - closed circuit rebreathers fluctuate greatly.  Generally, however, you are going to join the counterlung (or lungs) into the absorbent canister and then put in them at the framework of the rebreather.  You'll test the one time valves at the ducts and then attach them into the counterlungs. You can set up the canister (s) and assess their valves.  This could demand twelve hose links.

Still another is you can not impact your buoyancy by inhaling or exhaling, as the exact identical quantity of air simply goes backwards and forwards between your own lungs and also the rebreather rather than affects volume or buoyancy.  If you should be utilized to exhaling to obtain below the surface, then that wont do the job.

If you're intending yet another dip that afternoon and also have enough petrol and scrubber time , whatever you have to do would be to turn the rebreather off throughout the surface interval.  It's really a fantastic strategy, though, to inspect the breathing loop to get water indoors.

Additionally, while you descend as well as the counterlungs enlarge, the rebreather will port gas. This really could be the only real time that the rebreather purposely disturbs a substantial quantity of gas, and also why"saw tooth" profiles are particularly ineffective. You may likely realize that the rebreather doesn't port gas fast and you also become buoyant, and that means you ought to manually ditch from the BC, your drysuit or by the rebreather.

Then you'll examine the full unit for air escapes and water flows.  Leaks are potentially severe.  You've little gas up to speed you can not afford to drop any.  If water flows cause the machine to flooding, it is going to end up exceptionally negative.  And water from the CO2 scrubber induces a reaction with an sterile referred to as a"caustic cocktail"--an awful mouthful that could burn your own lips, throat and mouth.

At the start of an ascent onto a semi-closed-circuit rebreather, then you also have to purge the loop to enhance your breathing mix.   Closed- circuit methods add oxygen .

For those who experience an oxygen track and other electronic equipment, you also are going to test them.  When you get a constant-flow semiclosed rebreather, then you'll want to inspect the leak rate of this orifice.

In case this can be the very final dip for a couple of days, you need to disassemble and wash out the rebreather thoroughly.  The hot, moist environment within the lymph is excellent for growing bacteria, therefore it has to be disinfected with all the remedy that the manufacturer urges, subsequently rinsed well and dried.  Drying the interior the breathing loop, even having its baffles and corrugated hoses, which can be exceedingly hard.

Should you work remarkably hard--when you've got to swim against a current, such as --your own body will simply just require oxygen from their breathing loop faster than usual. Closed circuit passive and systems semiclosed-circuit systems will feel that this and add extra oxygen.  Active semi-closed systems may not, nevertheless. If that's the instance you must be sure to"purge the breathing loop" by massaging this oxygen-poor gas throughout your nose therefore that the rebreather replaces it using wealthier gas.

The used CO2 absorbent must be dumped and the scrubber canister has to be thoroughly dried and cleaned.  Electronics and oxygen sensors have their particular care requirements.  Plan on spending one hour postdive maintenance in the beginning, though you're going to get faster without experience.

Somewhat harder self-mixing semiclosed-circuit rebreathers add oxygen and a diluent separately through fixed orifices or (regarding this diluent) a demand valve.  They also may use less gas, but might be subject to larger variations in the air content of this gas mix.

Fully closed circuit rebreathers aim to control the oxygen content in your breathing gas.  They add only the gas you require, when you need it, and do not waste any.  Ergo, zero bubbles the majority of that time period and also a longer gas duration. This fine control of gas inclusion comes from a electronic wizardry.  Normally, detectors analyze the oxygen of the lymph and also in form a computer, that adds oxygen diluent as needed to keep a preselected"set point" to your oxygen partial pressure.  Redundancy (frequently three oxygen detectors and two computers) creates the wiring and plumbing diagrams confusing, but the idea is fairly easy.  

Semiclosed-circuit rebreathers have the simplest gas controller mechanism.  Fundamentally, it is simply a fixed orifice, an opening that enables a continuing flow rate into the respiratory tract.  Any excess above that which the system absorbs is vented to the water in a stream of small bubbles, and that's the reason why the device is called"semiclosed."

On both sides of the scrubber there is a counterlung, just a flexible bag that expands and contracts to adapt the exact on/off nature of your breathing.   The counterlung in the side has a input where more oxygen or nitrox is added.

Oxygen sensors have a life span and have to be replaced, usually every 12 to 24 months, based on just how far that they used.  (They deplete themselves in atmosphere about 50% as fast as when stirring.)  After diving, some divers remove them by the rebreather and seal them to extend their own life.

Exactly how many electrons have been injected in to the inhalation counterlung, and also the way the injection is controlled, determine whether it's semiclosed-circuit or closed-circuit.

Some manufacturers recommend that the entire unit is given a comprehensive review and overhaul every year.

Long Term Maintenance

Each canister has a first and another stage regulator that demands annual support.  These are typically just normal open-circuit regulators which can be serviced by the local dive shop.  Cylinders need to be hydro tested and visually inspected like some other person.

Each of of rebreathers are built around the principle of a one-way breathing loop.  One hose takes your exhaled breath to the CO2 scrubber, and the other brings back it (without the CO2) for a mouth.

"Passive" semiclosed-circuit rebreathers inject petrol just ondemand.  Numerous mechanisms to trigger the gas injection could be used, nevertheless they are mechanical.  By way of instance, a system of ratchets and levers measures how big a counterlung, when it gets below a specific size (because the body has removed that much oxygen out of the breathing loop), it activates a valve to inject further gas.  Passive systems use less gas than busy ones, however the actual material of the gas mixture from the breathing loop might be more variable.

The Drager Dolphin and Ray are popular instances.  They are called"mass flow" or even"active" semiclosed-circuit rebreathers--active as the unit is definitely injecting brand new gas.  The orifice, which controls the flow rate, needs to be selected before the dive to coordinate with the nitrox mixture chosen.  This type of rebreather is on or off: Whenever the air valve is fired up, gas flows in to the breathing loop at the rate determined by this orifice. Manual inclusion valves and also another plumbing might complicate the picture, but that's the nature.

Computer controls have batteries that have to be replaced periodically.

Insert a mouthpiece using a valve to reduce flood, a one time valve in each breathing hose therefore that your breath circulates the perfect way, and also several other equipment and you have a basic rebreather.

If you're diving tomorrow, however, you'll need only disinfect the mouthpiece and corrugated hoses.

Are You Really Ready To Get a Rebreather?

Are you currently self-disciplined?  Pre-dive, through the dip and postdive you must make up the brain to check out procedures and checklists exactly.  Filling the scrubber canister and building the breathing loop until the dip involve measures that have to be followed and evaluations which can not be skipped. Exactly the same care has to be obtained if cleaning and interrogate the rebreather after the dip.  And through the dip you've got to view gauges more tightly compared on circuit.  Are you really meticulous concerning maintenance of one's open circuit gear, as an instance, or would you"hose and proceed"?

Rebreathers promote what is called"mission creep" A number are effective at dives far beyond the practice of the majority of recreational sailors.  Components that could modify the gas mixture throughout the dip are specifically appropriate to decompression diving.   You are going to discover just how to work the system, however maybe perhaps not the particular areas of technology diving such as heavy diving and cave consciousness, such as.  "Mission creep" usually takes the seemingly benign type of adding additional non-technical but rough gear too so on.  Employing a intricate camera rig may divert you in tracking your rebreather attentively, such as.  

You'll want to appear not within the rebreather but on your own.  Some personality types are more satisfied than the others to the requirements of caring and using to get a rebreather.  And a few folks probably shouldn't consider it.

Can you accept liability for the own safety?  You've got to choose the attitude that the right performance of one's rebreather is dependent for you alone.  The thought that producer, the instructor or another person is responsible could be satisfying for your heirs but won't keep your own life in case of a collapse. Have you been familiar letting the ship team or a dive buddy put your open circuit gear for you personally, or can you insist upon doing this you?

Rebreathers are somewhat more technical than open circuit set ups, and you'll need to be self-explanatory for meeting cleaning, maintenance and plenty of the repair, as the odds of the community dive shop with an expert are slim. Even the easiest rebreather on average has each of the sections of one's open circuit installation, and far more. These parts, and also the relations between them (you will find 50 or even more o rings in a normal rebreather), will need to have routine care.