10 Things to Know Before Buying a Rebreather

Words and Photography by Jill Heinerth

Rebreathers offer an entirely new way to enjoy the underwater world. Whether it is the technology that attracts you or the potential to swim free without making bubbles, the decision to enter the domain of rebreather diving is a significant one. You will be making a considerable investment in equipment and training, in addition to taking a serious look at risk assessment. It can be hard to know where to start. 

There are dozens of manufacturers making rebreathers around the world, and comparison shopping is almost like buying a car. Dozens of different car makers manufacture vehicles ranging from small smart cars to big trucks. Some cars run on gasoline or diesel, and others employ hybrid technology. Regardless of their differences, cars and trucks have many similarities and also contain common subsystems. Each car, motorcycle, or truck has wheels. Each vehicle has an engine and brakes. Some vehicles have extra features like airbags, and anti-lock brakes, and sophisticated locking mechanisms. Ask “Which car should I buy?” and the answer might be, “It depends.” The same is true for rebreathers. 

Different rebreather models are equipped with a wide variety of subsystems, mechanisms, and features. You don’t need expert knowledge to make an informed purchase decision, but the following points should help steer you in the right direction.

Rebreathers are designed to recycle the gas that an open-circuit diver typically would exhale into the water column. This action conserves gas volume, reduces the noise made by bubbles, and extends the range of a given dive. Rebreathers are operated either manually or automatically, and are built by numerous manufacturers offering different operational designs. 

Exhaled gas is captured within a breathing loop. Thanks to one-way mushroom valves, the gas travels through the loop in only one direction. The breathing loop is furnished with one or two flexible counter lungs that help compensate for the changing gas volumes that occur through the respiratory cycle. Gas is routed through the scrubber, which contains an absorbent material that removes the carbon dioxide from the exhaled breath. After dwelling in the absorbent canister for a precise amount of time, the gas passes over one or more oxygen sensors. Based on information gathered by the sensors, either the diver or the electronics package intervenes and adds oxygen to replace that which has been metabolized by the diver. If the level warrants, it may be added with an injection or flow of oxygen or other high-PO2 gas, bringing the life support levels back to a suitable or selected point. The gas may then pass through another flexible inhalation counter lung and then through a one-way valve back to the diver’s mouth. When diving a rebreather, you are able to control your life support environment, perhaps the most dangerous thing you will ever do. As such, choosing to buy a rebreather is a decision that must be made with respect to risk.

1 The decision

Determine if you are ready to be a rebreather diver. Consider the risks and rewards and discuss them with your family. At the time of this writing, rebreather divers were ten times more likely to have a fatal accident than open circuit technical divers. If you are diligent with protocols, the additional risk can be mitigated, but the ultimate choice to buy a rebreather is one to make with your entire family. Ensure you have all the needed prerequisite training and experience completed. This is not a time to be struggling with academic knowledge or diving skills.

2 Learn about how rebreathers work

Bone up on your knowledge about how rebreathers work. The basics will suffice. Get a book, attend a seminar or seek out a mentor. You will need to know a bit about mechanics so that you do not get sucked in by a biased sales pitch. There is no perfect rebreather, but you can find the right rebreather for you if you are willing to do a little work.

3 Establish your budget

Determine your initial investment budget and operating/maintenance budget well in advance. This will help you narrow the choices and make a decision about whether you can afford new or will be buying a pre-owned unit. Consider the cost of the rebreather, bailout devices, and training. You may have to travel for training, so consider that, too. Once you are qualified you will have continued costs for consumables such as batteries, sorb, gas fills, oxygen sensors, spare parts, and annual maintenance.

4 Learn about how rebreathers are made and tested

Buy a rebreather from a reputable manufacturer. If you are going to spend upwards of $10,000, you deserve to be diving a piece of equipment that has gone through proper third-party testing and validation. In North America, there are more regulations regarding the manufacture of toasters and hair dryers than there are for underwater life support. That means you need to do a little more diligent searching for information. In Europe, rebreathers must conform to a standard called CE 14143 and will bear a mark indicating such achievement. That means you can get evidence of tests ranging from work of breathing to manufacturing tolerances and sensor tracking, proving an agreed upon level of safe operation. Without third-party independent testing, you are essentially putting yourself in the position of serving as a test pilot without a helmet or seat belt. In my opinion, a manufacturer that sells life support equipment should invest in reaching this high bar of excellence. Life support equipment should be appropriately vetted, tested, and verified for safety. 

5 Find a good instructor

Even before you purchase a unit, determine if there is a suitable instructor available to you. Interview potential instructors to assess their experience and up-to-date continuing education on the unit that you would like to buy. Rebreathers are not overly complicated, and your instructor should have real-world knowledge developed by a lot of time diving the particular unit that you are interested in using. If they do not have at least 100 hours on that model, they may not have had a chance to deal with some of the subtle failures and tricks that can be passed along to you through experience. Good, experienced rebreather instructors are few, and in great demand. Reputable instructors have busy schedules that may require booking up to a year in advance. Professional instruction will not be cheap. You must be willing to support a level of excellence that you expect from a rebreather instructor who will be teaching you about life support and survival. This is not the place to cut corners on your budget.

6 Determine where you will get support

If the rebreather you would like to buy is manufactured overseas, it may need to be serviced overseas, even if there is a local distributor. Understand where and how service occurs. How long will it take? Will you be shipping a heavy box halfway around the world and waiting months for it to return? How much work can you do yourself? Are other divers having problems that require a lot of service support? Are parts generally available? Has the manufacturer been around for a while? Are they a stable, well-funded company?

Having local support and role modeling from dive shop mentors or experienced locals on a particular unit is worth its weight in gold. If everyone in your dive club owns one type of rebreather, then you should give it a hard look. Having role models, spare parts, and dive boat support is extremely valuable.

7 Decide on the features you want

Choosing a unit is a tough decision, and nearly everyone you ask for an opinion will have a strong one. You have to remain pragmatic and analytical. A try-dive experience will only help you fall in love with a well-fitted harness. A comparison of cosmetics will merely help you decide whether you will look cool. Take time to compare features and research the unit on your own before jumping into one of the most significant purchase decisions of your life.

Some rebreathers are more manual and others have a high degree of electronic control. That does not necessarily mean that one is safer than another. Analyzing accident and incidents over the past twenty years, researchers like Dr. Andrew Fock have determined that there is no particular brand or style that causes more fatal accidents than another. It appears that most accidents are caused by diver error and poor choices. That means that your purchasing decision will not be driven by “this is safer than that one.” Salespeople who make that claim are ill-informed. Features like sophisticated alarm systems and carbon dioxide sensing come with a price. You should decide which features are most important to you and your style of diving. This may include researching accessories that you might want to add. An off-market bailout valve (BOV) or Near Eye Rebreather Display (NERD) will add to your investment, and you should also research their compatibility. There are many amazing rebreather add-ons that might interest you down the road as long as your rebreather is compatible. This includes compatibility for trimix diving. Learn about the operating time, depth rating, and gas compatibility specifications of your unit. If the rebreather is not rated for 330 feet (100m) depth, it is not necessarily a mechanical issue such as crush depth. The rebreather may not be capable of delivering a safe work of breathing if you go deeper. Ensure that you know what you are buying by reading manufacturer’s specs. The internet is not always a reliable source of information. Just because somebody survived a dive to 400 feet (120m) does not mean the rebreather is safe to use at that depth. Beware of anecdotes. Search for hard evidence such as data from CE testing.

8 Decide if you will want to travel with your rebreather

Most airlines have extremely stringent baggage restrictions and some rebreathers are more portable than others. Generally, a 50 pound (23kg) bag or box can be shipped on a passenger aircraft without exponentially high charges. Will your unit break down into a shipping case that fits the weight and size requirements for most airlines? You won’t be traveling with your tanks, so just look at the rest of the unit. How much extra gear, spare parts, and tools will you need to take? Determine the total weight so you understand the costs of travel.

9 Consider buying a used rebreather

There are many places where you can buy a certified used rebreather from a manufacturer. Some private sales offer the assurance that a rebreather has been recently serviced. If you buy used, check that you are not buying obsolete. If a rebreather becomes obsolete, you may not be able to get the necessary parts or support to keep it operating. However, a lightly used unit from a reputable manufacturer might be a good buy if it has been serviced. Check with the manufacturer to ensure they will service the unit in the future if you are the second buyer.

10 Resolve to dive with strict safety protocols

Before you purchase a rebreather, look deep into your diving past to determine if you are going to be a diligent diver who respects protocols and is willing to skip the most exciting dive of your life. If you don’t have a high level of discipline and a respect for safety rules, then you shouldn’t buy a rebreather. If that is the case, stick to open circuit (OC) scuba, which is generally more forgiving. When a problem happens on OC, the diver is usually alerted with a “boom, hiss,” from loss of gas. Rebreather problems are much more subtle and slow to develop. If you are attentive, you usually have a long time to find a problem; but if you are complacent, it is easy to miss a developing issue that could cost you your life. Rebreather diving is not for everybody. It requires substantial personal investment and dedication to safety.

Rebreather diving gives us a chance to have unequaled experiences with wildlife. They offer us increased depth and time range and when used correctly can be safe and enjoyable devices that take us to new horizons. With well over twenty years of rebreather experience, I still view my rebreather as a tool with a purpose. I don’t use it on every dive. It is not always the right gear for the job. However, I have been able to achieve things that would have been impossible on open circuit. Whether spooling out an exploration line in the back of a virgin cave or getting close to an enormous manta ray, I have enjoyed the possibilities that rebreathers have given me in my career. Make a thoughtful choice, and your rebreather can last you for a decade or more. Dedicate yourself to safe diving protocols and require them of the people that dive with you.