CCR FAQ - Poseidon Se7en

Prepared by Mark Derrick, CCR Instructor on Staff

How much does a Poseidon Se7en cost?

A better wording of the question might be 'How much does it cost to switch from an open-circuit diver to a rebreather diver?' The price of the rebreather itself can vary significantly depending on configuration options. Plus there are usually additional equipment purchases depending on what existing gear you have that can be re-purposed. Training, particularly if travel is required, will be a significant cost. I suggest planning on a total amount of about $10,000.00 to $15,000.00, with around $12,500 being fairly typical.

How long does it take to get a Se7en rebreather?

Poseidon Se7en rebreathers, along with all options, accessories and spares will usually be in-stock for immediate shipment. Occasionally, demand or logistics will cause brief stock-outs of the base unit but delays beyond 30 days are rare.

How much does the Poseidon rebreather training cost?

There is wide variation in training costs due to a variety of factors, although location is often a major influence. There is a geographically diverse group of instructors and you might have an instructor in your local area. Typically, the cost ranges from $1000 to $1500 for instruction only, plus out-of-pocket costs. If you prefer to learn about your rebreather at Dive Gear Express in Pompano Beach Florida, training can be organized to accommodate your schedule and rebreather courses run every month.

Can I buy the rebreather without training?

Yes, but you won't be able to dive the rebreather until you are trained. Every rebreather requires formal, model specific, training in order to competently dive with the equipment; ordinary open-circuit training is not adequate. If you are not already certified for the rebreather, per manufacturer requirements you will receive a disabled unit that can only be enabled by your instructor. Once you complete training, your instructor will permanently enable your unit.

How much does routine maintenance cost?

You should budget routine maintenance costs of approximately $400 annually. Poseidon recommends the two oxygen sensors be replaced annually. You will also need to replenish minor consumables such as lubricant and disinfectant from the annual maintenance budget. The rebreather must be returned to an authorized service center approximately every 24 months.

What consumables do you recommend?

The recommended consumables are: Molecular Products Sofnodive 797 absorbent cartridge, Steramine for sanitizing the breathing loop, Tribolube 71 O2 Compatible Lubricant for O-ring seals, Caig Labs DeoxIT GOLD for cleaning gold electrical contacts, and Analytical Industries PSR-11-39-MD diving grade oxygen sensors.

How much do the consumables cost?

As with all rebreathers, the major consumable cost is CO2 absorbent. An absorbent cartridge is about $35 and typically can be used for several dives, but there are other smaller costs such as gas fills. Keep in mind that for both open-circuit and rebreather divers, consumables costs are usually insignificant in relationship to the investment in the equipment, training and other diving costs such as boat charters and travel.

How long do the consumables last?

When tracking their CO2 production by monitoring their O2 consumption, divers are reporting scrubber durations in the range of four hours, if determining duration by wall clock time only then the absorbent duration is three hours. The durations in actual use depends upon many factors related to the individual diver and specific dive conditions. These are observations of what experienced divers are reporting and in no way suggests exceeding manufacturer recommendations or that novices should expect these durations.

Why use a prepacked cartridge CO2 absorbent instead of loose granular?

The Poseidon rebreather is designed to use the Sofnodive 797 cartridge CO2 absorbent manufactured by Molecular Products. Cartridges solve many of the problems associated with traditional loose granular carbon dioxide absorbent. The cartridge absorbent uses the same chemistry as loose granular absorbent but in the form of easy-to-use cartridges that are quickly loaded into the scrubber canister. The individually sealed cartridges need only be opened immediately prior to use and are date stamped to assure freshness. Cartridges eliminate problems of channeling and duration variability associated with granular absorbents because they eliminate both settling and individual differences in canister filling technique, delivering more consistent performance.

Is the cartridge more expensive than granular?

Compared to granular, the cartridge costs about $5 more per hour of sport diving using a duration of three hours and less with longer duration. But even assuming the cartridge is more expensive than granular, this is justified because the cartridge absorbent offers important and valuable advantages over granular.

What about the possibility of a 'caustic cocktail' with the Se7en?

Inhaling a mixture of CO2 absorbent and water while diving is very unlikely. The Se7en is a modern CCR design that includes several features to manage and remove water from the breathing loop. The Sofnodive cartridge also includes a hydrophobic barrier, even further diminishing the risks. The 'caustic cocktail' is a concern from an earlier era of rebreather diving that has been overly dramatized, akin to the concern new divers express regarding 'shark attack'.

How available is the absorbent cartridge?

In the global economy, absorbents are sold and shipped all over the world. As a result, supply logistics for absorbent is becoming less of an issue. The number of dive shops that stock absorbent is consistently growing, and you can always order on-line to be delivered to your door or directly to your travel destination. Unlike loose granular absorbents, transport of the cartridge rarely raises hazmat objections by carriers and often costs less to ship.

What about Solid State Oxygen Sensors?

The Poseidon Solid State Oxygen Sensor (SSO2) offers the benefits of no need for routine calibration, no need for periodic annual replacement and enhanced stability. Dive Gear Express believes the SSO2 has to potential to offer enormous improvement in convenience and reliability of oxygen measurement for divers. The digital SSO2 is not a plug compatible replacement for an analog oxygen sensor and so currently the only device that can use the SSO2 is the Poseidon M28 dive computer in a monitoring only application with the Digital CPOD. In mid 2018 the Poseidon rebreather electronics head will offer a electronics upgrade to enable it to use an SSO2 to control the oxygen level of the loop. As with any cutting edge new technology only time will tell how this shakes out, and we currently do not recommend starting out with solid state sensors.

Does the Se7en have a CO2 monitor?

No. CO2 monitoring is a 'bleeding edge' technology that will begin to appear in recreational rebreathers in the next few years but as a practical matter the merits of CO2 monitoring are unproven. You should not confuse a CO2 monitor with the breathing loop temperature monitor or the scrubber temperature monitor offered by rebreather manufacturers. The temperature monitor does not provide any information or warning regarding actual CO2 levels in the breathing loop.

What battery module should I choose?

The basic rechargeable smart battery Rec 40 (aka Green) supports sport limits of no-stop required dives to a maximum of {132 fsw | 40 msw} on air diluent. Poseidon offers a selection of other batteries (identified by their color) that each enable software features which allow progressively more advanced levels of diving. Because these batteries are expensive and time consuming to later upgrade, for divers who expect to exceed sport limits we recommend always initially choosing the Deep (aka Black) battery that unlocks all functionality and has no depth or gas mixture restrictions.

What cylinders should I use?

The rebreather will accept 2L or 3L cylinder sizes using standard 'inline' DIN valves. For all divers, we recommend the Poseidon QMR cylinder mounting kit and the Poseidon cylinder inversion kit options. Smaller stature divers may prefer the 2L cylinders and the 3L volume diluent cylinder has adequate on-board bailout capacity for sport diving in {60 ft | 20 m} or less, although I strongly recommend carrying off-board bailout on all dives. Aluminum 13 or 19 cubic foot (2L or 3L) capacity cylinders minimize the total weight, but most divers find they must add weight to adjust their in-water buoyancy and trim. The rebreather may also be configured with steel 17 or 23 cubic foot (2L or 3L) cylinders, and these are the cylinders I generally recommend. Most wetsuit divers find having the steel cylinders requires little or no additional weight and trim can usually be made perfect simply by slight adjustments to the mounting height of the cylinder.

Which style of counterlungs should I choose?

Over-The-Shoulder (OTS) vs. Back-Mounted (BMCL) counterlung configurations have subtle trade offs of one benefit for another, and the choice is more complex than can be answered briefly. Conventional wisdom says, all other factors being equal and in most circumstances, over-the-shoulder offers better work-of-breathing than back-mount. For rebreathers in general, OTS counterlung configurations are the most popular and usually considered easier to manage. The Se7en BMCL option is a very recent introduction which does not yet offer a manual gas addition solution, which in my opinion limits BMCL to sport diving only. Many professional photographers have a preference for BMCL, but for diving where performance and safety is paramount I recommend an OTS configuration with the manual addition valves option.

What BC should I use with the Se7en?

The Poseidon "jacket style" Rebreather BCD with integrated OTS counterlungs is a viable option for divers who expect to remain within recreational sport limits. However, we suggest a harness, backplate and wing (BPW) style system that mounts using standard 11-inch centers. We generally recommend the very comfortable Dive Rite TransPac, adding a ring bungee to sidemount your bailout. The Dive Rite CCR Wing has a shape and features that work well with the Posiedon and offers very low drag. The CCR wing offers { 50 lb | 22.68 kg } of lift and technical divers should consider the redundant bladder option. Poseidon also offers a harness, backplate and wing BCD system if you prefer to remain with a single vendor. Regardless of your choice, you will require either the Poseidon BCD quick-mount-release option (recommended for sport) or the Poseidon 11-inch Adapter option (recommended for tech).

Does the Se7en accept an additional independent Oxygen sensor?

Technical divers will be pleased to know there is an option for adding an independent oxygen sensor to the inhalation side of the breathing loop. We can deliver your Se7en customized with a special third sensor adapter that connects to the Poseidon M28 handset.

What is the Se7en maximum dive time and depth?

Rebreathers carry many hours of breathing gas regardless of depth, so the dive time is rarely limited by gas volume. As with most rebreathers, the Se7en diver is typically limited by the duration of the CO2 absorbent, so multi-hour run time dives are routine. As with open-circuit nitrox diving, rebreather divers must also monitor their decompression and oxygen exposure; depending on the dive profile these may also limit the dive time. The Poseidon rebreathers are suitable for diving at all sport depths and the Se7en with the Deep battery has been qualified to a depth of {330 feet | 100 meters}. Although the Se7en can function at depths beyond sport depths, as with any rebreather there are numerous additional considerations. .

Is the Se7en capable of diving with mixed gases?

Yes, the Se7en with the Deep (aka Black) battery can use either nitrox or trimix diluents that may be either hyperoxic, normoxic or hypoxic. Because the Se7en is a fully closed-circuit design, the use of mixed gas diluents is very inexpensive compared to open-circuit. Personally, I recommend and teach rebreather divers to substitute normoxic trimix diluent (21% oxygen, 35% helium) rather than air even within recreational sport limits for the benefits of reduced narcosis, improved work of breathing, and improved scrubber function. However, use of anything other than normoxic diluent or diving outside of recreational sport diving limits requires significant additional diver training.

Does the rebreather take a long time to maintain?

Yes and No. Many rebreather sport divers, including Poseidon divers, find they spend noticeably more time on equipment compared to open-circuit because the rebreather diver must always be careful and disciplined about maintenance. If you have been habitually careful with your open-circuit dive equipment and treat your equipment with respect, as an experienced rebreather diver you will spend only slightly more time with your maintenance than you did with open-circuit.

How well does the Poseidon rebreather travel?

The Poseidon rebreather is very travel friendly. A key design goal was to minimize size/weight and divers are able to travel by air with it as carry-on luggage in most circumstances. Regardless of the brand of rebreather it can be annoying to travel with cylinders because they are carefully examined by security personnel, and occasionally even confiscated. You may prefer to rent cylinders at the destination or ship your cylinders ahead.

How is the Poseidon different from other rebreathers?

All of the major rebreather models are good quality units. There is no perfect rebreather; they all have strengths and weaknesses that make each uniquely more or less suited to your needs. The Poseidon Se7en a richly featured and proven design with good redundancy from a well established manufacturer. The Poseidon is a European design that favors the sport diver with intentions of continuing on to technical diving, and offers some of the most advanced technology in the market. It is an exceptionally automated design that is smaller, lighter and simpler to use than many other rebreathers. It is a robust eCCR choice that will take you as far as you wish to go in general sport and technical diving. As an independent dealer, we stock spares and consumables with online ordering and same day shipping.

Is the Poseidon rebreather safe?

No type of rebreather can be said to be categorically safer than another. No rebreather is foolproof, and the fact remains that compared to open circuit there is a disproportionate number of rebreather fatalities, many of which have been attributed to diver error. The quality of training may be the most significant factor affecting rebreather safety. Your safety while diving is controlled by you, not by your rebreather.

Last Updated: 10-Feb-2018

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