Review: Kiss Rebreather and Megalodon Rebreather
With rebreathers now an established part of the diving scene, interest is no longer strictly limited to the Buddy Inspiration. Experienced technical divers give the low-down on two new ‘alternative’ rebreathers
Sealed with a KISS:a rebreather revolution
One of the best-kept secrets in the diving business over the past year has been the KISS rebreather. This closed-circuit rebreather has a growing following of owners and yet there has never been any public launch or hype. News of this rebreather has spread by word of mouth. There is now a core of enthusiasts who dive the KISS and, with more than 50 units now in use, the KISS is quietly evolving into a mainstream unit that is especially popular with the technical, deep and cave-diving communities.
KISS manufacturing is based in Vancouver and is masterminded by diver and designer Gordon Smith. He set out to build a rebreather that was as simple as possible (hence the KISS name-tag, which stands for ‘Keep It Simple, Stupid!’), yet which incorporates ruggedness and redundancy and does not rely on computers to control the breathing mix. The resulting unit is fully closed and uses a novel, metered orifice and an uncompensated first-stage regulator to supply oxygen at a preset rate that approximates to the expected metabolic rate of the diver. Any differences on a dive are manually adjusted using an override injection control.
As supplied, the metered orifice allows the KISS to be dived to a maximum depth of about 60m. If the orifice is replaced by an alternative smaller item and the supply pressure of the oxygen is readjusted to suit, then the KISS can be dived to a depth of about 100m without further modification. However, one KISS rebreather has been further modified to reach depths well beyond 100m, simply by adding an additional first stage that is depth-compensated.
The oxygen partial pressure is measured by three totally independent displays mounted on the diver’s wrist. But it is important to appreciate that there is no automatic control of the oxygen partial pressure. If one oxygen cell reading deviates from the other two, it is up to the diver to decide which cells are displaying the correct reading rather than relying on the ‘majority vote logic’ incorporated by the computer systems of rebreathers such as the Buddy Inspiration, the Prism and the Biomarine Mark 15.5.
Similarly, if the oxygen partial pressure rises too high or drops too low, there are no alarms to alert the diver and no injection solenoid to correct the problem. The entire ethos of diving a KISS is that it is the diver who is in control and who takes full responsibility for checking and correcting the partial pressure to the desired level. Deeply engraved on the back of every KISS unit is the warning ‘Danger! This device is capable of killing you without warning’. Surely this is the ultimate product liability statement!
In practice, however, diving a KISS is surprisingly simple and stress-free. Unlike over-the-shoulder counterlungs on some other rebreathers, the back-mounted counterlungs of the KISS give a free and uncluttered chest area. While this does not give identical breathing characteristics in all diving positions, the KISS nevertheless breathes exceptionally well and is a pleasure to dive. It also includes some very useful features as standard, such as automatic diluent addition and an integrated open-circuit bail-out mouthpiece.
The KISS rebreather is not a CE-certified unit, so individuals must import their units directly from Vancouver. The rebreather comes as a kit, with all critical O-rings deliberately left unfitted. Each owner must strip and rebuild his unit to fit these O-rings, thereby ensuring that he or she has a complete understanding of how the rebreather works before being able to dive it.
Configuration of the KISS rebreather is very much a function of how the owner wants it and there are a variety of different-looking units in use. Owners must provide their own backplate, harness and wings, and their own cylinders. Two Apeks regulator first stages must also be provided. Some units utilize small, 1-litre cylinders for no-decompression diving, while other divers prefer much larger cylinders, to allow sufficient bail-out capability for deeper trimix dives.
• The basic KISS kit costs about £2,500, once imported into the UK. For the cost of regulators, cylinders, backplate, harness and wings (if you do not already have them) add about £1,000 making a unit ready-to-dive for around £3,500. For more information contact: Jetsam Technologies on tel: 001 604 469 9176, email: email@example.com or see the website: www.jetsam.ca
Mega-dive: the Megalodon closed-circuit rebreather
The Megalodon is a new rebreather which has taken the American cave-diving community by storm. It is now available to all, but because of its popularity there is a long waiting list.
So why did I decide to go for the ‘Meg’? I was attracted by its high-quality engineering, as well as the manufacturer’s reputation for excellent customer service. Designed by Leon Scamahorn (a US Army special forces veteran) of Innerspace Systems Corp, alongside engineer Morgain Harris, the unit is very small and very simple. It can take its users to a maximum of 150m, and the CO2 scrubber allows a duration of four hours (Innerspace is working on a radial scrubber that will allow longer dives). In my opinion, it can be safely used from sports diver level upwards.
The unit itself consists of an aluminium canister (it comes in two sizes, large or mini-Meg), which contains all the electronics and 500-hour batteries. The unit also has its own decompression software. It works with a tertiary redundant-oxygen-sensor display and an automatic diluent-addition system. Any size of diving cylinder can be mounted to the outside of the canister and there are over-the-shoulder neoprene counterlungs, which can be easily attached to any type of wing and harness. We bought new wings and harnesses from Custom Divers, which were ideal for the job.
People have a way of talking rubbish when it comes to rebreathers. The fact is that they are actually quite easy to use, and therein lies the danger – they are almost too easy to use. The key to using rebreathers is to remain vigilant and continually monitor the oxygen levels on the display, because too much or too little oxygen can lead to death underwater. As with most rebreathers, the Meg requires meticulous daily preparation: scrubber filling, cleaning, greasing O-rings are all part of the routine. But the important part is that none of this preparation work is particularly difficult – it just has to be done methodically.
The key skills of the course are emergency drills to deal with the various problems which can theoretically arise with rebreathers – hypoxia, hyperoxia, CO2 build-up and loop flood are the main drills, which we practised four or five times on each dive. The Meg weighs 26kg and is compact and easy to wear.
It’s certainly lighter than wearing twin 12-litre cylinders with twin 7-litre sidemounts. At the moment, courses are not available in the UK – the current instructors for the Meg are all based in the US or Thailand.
• The Megalodon closed-circuit rebreather costs $6,500 (about £4,040), plus training courses and shipping. For more information contact: Innerspace Systems Corp on tel: 001 360 330 9018, email: firstname.lastname@example.org or see the website www.customrebreathers.com/products.html