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How much does an Sentinel cost?

A better wording of the question might be 'How much does it cost to switch from an open-circuit diver to an Sentinel CCR diver?' A complete ready-to-dive Sentinel Level 1 unit with cylinders, harness and wing is about $9,000 and to this you might add: off board bailout about $500, and initial stock of consumables about $300. Training, particularly if travel is required, will be a significant cost. I suggest planning on a total amount from $11,000 to $13,000. If you expect to purchase Level 2 or Level 3 versions, these additional costs should also be factored into your budget. These are estimates, the total could be less or more depending on what suitable equipment you already have and what additional equipment you might choose to purchase.

How long does it take to get an Sentinel rebreather?

The Sentinel is currently in production, with approximately 4 to 6 month lead time from order, by 2009 the lead time should be more like 30 to 60 days. Once order backlogs are satisfied, the Sentinel rebreather, along with all options, accessories and spares will be in-stock for immediate shipment and also available for local pickup at Fill Express, our local dive shop in Pompano Beach, Florida.

How much does the Sentinel training cost?

There is wide variation in CCR training costs due to a variety of factors, although location is often a major influence. At Fill Express the cost is $1500 for instruction only. Fill Express also offers an all inclusive version which includes the cost of pool rental, consumables, teaching materials, boat charters, and so on for a price of $2000. There is a geographically diverse group of instructors and you might have an Sentinel instructor in your local area. If you prefer to learn about your Sentinel at Fill Express, training can be organized to accommodate your schedule and rebreather courses run every month.

How much does Sentinel routine maintenance cost?

You should budget routine annual maintenance costs of approximately $500 annually. As a general rule you will need to replace some rubber seals and the oxygen sensors approximately once a year, along with annual maintenance overhauls on the two gas supply first stage regulators. You will also need to replenish minor consumables such as lubricant and disinfectant from the annual maintenance budget.

How much do the Sentinel consumables cost?

As with all rebreathers, the major consumable cost is CO2 absorbent and the Sentinel can use several different forms of absorbent. The cost of absorbent will vary depending on variety of factors, but the range is from $20 to $30 per single load. A load typically can be used for several dives, but there are also 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 Sentinel consumables last?

The manufacturer recommends the Sentinel CO2 scrubber duration be limited to 180 minutes at 130 fsw, based on CE testing with a CO2 generation rate of 1.6 lpm in 39°F water temperature. In practice, typical warm water Sentinel sport divers can expect scrubber durations in the range of four to six hours and battery durations of up to 60 hours on a single charge. The durations in actual use depends upon many factors related to the individual diver, specific dive conditions and particular brands of consumables. These are predictions based on experienced divers and in no way suggests exceeding manufacturer recommendations or that novices should expect these durations.

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

Inhaling a mixture of CO2 absorbent and water while diving with an Sentinel is very unlikely. The Sentinel is a modern CCR design that includes several features to manage and remove water from the breathing loop. 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 Sentinel CO2 absorbent?

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. The Sentinel's flexibility to utilize a variety of absorbent form factors offers the benefit of the widest possible availability for CO2 absorbent.

Does the Sentinel have a CO2 monitor?

No. As a practical matter, there may be little value to detecting CO2 already in the loop as it could be too late to warn the diver in time to react appropriately. The Sentinel does incorporate a patented Temperature Profile Monitor (TPM) under license from the US Navy. The Sentinel TPM displays a thermistor based bar chart of the temperature profile through the filter to give the diver information on the activity of absorbent. The temperature monitor does not provide any information or warning regarding actual CO2 levels in the breathing loop.

What cylinders should I use with the Sentinel?

For Sentinel configurations I suggest the steel 15 cubic foot (2L) capacity cylinders (FX15), which minimizes the Sentinel total weight. The FX15's are more than adequate to support over three hours of sport diving, although I recommend an off-board bailout cylinder if using the FX15's. Most wetsuit divers using FX15's will find they will need only about 4 to 5 pounds for trim. The Sentinel may also be configured with a steel 23 cubic foot capacity diluent cylinder. With the FX23 cylinder, diluent capacity is sufficient to support on-board bailout for the sport diver and dry suit inflation.

What BC should I use with the Sentinel?

The Sentinel uses a special backplate that is included, along with a quick release style webbing harness and donut style wing. Although you can not use a standard backplate, you may use whatever style webbing harness you prefer. You might also take a look at the Dive Rite Nomad system; a modified version of the Rec Wing and TransPac harness that was originally intended for side mounting. The very streamlined design of the Nomad works well with the Sentinel and merits consideration by both sport and technical divers.

Does the Sentinel accept a fourth Oxygen sensor?

No, there are no provisions for a fourth oxygen sensor. A fourth cell is unnecessary in the Sentinel design because of it's sophisticated cell monitoring electronics.

What is the Sentinel maximum dive time and depth?

Rebreathers carry many hours of breathing gas regardless of depth. The Sentinel can accept auxiliary outboard plug-in gas supplies as well, so dive time is no longer limited by gas volume. As with most rebreathers, the Sentinel diver is typically limited by the duration of the CO2 absorbent, so multi-hour runtime dives are routine. As with open-circuit nitrox diving, rebreather divers must also track their decompression and oxygen exposure; depending on the dive profile these may also limit the dive time. The Sentinel rebreathers are suitable for diving at all sport depths and have been tested to a depth exceeding 300 feet. There are some individuals who routinely dive the unit that deep and deeper. Although the rebreather can function at depths much deeper, there are numerous additional considerations. The Sentinel rebreather is an excellent choice for divers who wish to dive to extremes.

Does the Sentinel take a long time to maintain?

Yes and No. Many rebreather sport divers, including Sentinel 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 Sentinel sport diver you will spend only slightly more time with your Sentinel maintenance than you did with open-circuit. In multi-dive days and multi-day diving, because the Sentinel rebreather needs very little attention between each dive in a series, considerably less total time may be spent on setup and maintenance than with open-circuit.

How well does the Sentinel travel?

The Sentinel includes a low weight travel box, such that less the loop and cylinders but including wing, backplate and harness, the unit is within the 70 pound limit imposed by most airlines. A separate bag is provided for the loop, and it can be packed in other luggage. 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 the cylinders ahead by a package carrier such as UPS or DHL.

How is a Sentinel 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. Beyond the features of the rebreather itself, you should consider the supplier along with how the model was designed and has been supported. Only a very few rebreather models are supplied by large and well-established dive equipment companies, and the Sentinel is the only rebreather where the electronics system has been developed by a leading dive computer company.

Is the Sentinel rebreather safe?

The Sentinel is a tested modern electronic CCR design. One expert on recreational sport and technical diving has said closed-circuit rebreathers are safer than open-circuit for the diligent diver. No type of rebreather can be said to be categorically safer than another. The quality of training is a major factor affecting rebreather safety. No rebreather is foolproof, and the fact remains that compared to open-circuit there are a disproportionate number of rebreather fatalities; nearly all of which have been attributed to diver error. Your safety while diving is controlled by you, not by your rebreather.