TecEvolution Pattaya Thailand: Rebreathers Information

Let's start at the beginning, what is a rebreather ?

Today, most diving apparatus falls into a class known as open circuit scuba; These are so called because every time the diver exhales, the inhaled gas escapes under the form of bubbles and is definitely lost to the diver.
This is where Rebreathers come in. The principle of a rebreather is to recycle partially or entirely the exhaled gas. To do so, the diver breathes on a loop, inhaling on one side and exhaling on the other. This is a transparent process for the diver ensured by one way, non return, mushroom valves forcing the gas flow in a single desired direction by preventing the gas to come back from where it came from. The gas then flows through a filtering canister called a scrubber, that removes the exhaled carbon dioxide (CO2) and is stored into a bag called a counter lung. When the diver inhales again, he can breather filtered gas from the counter lung and the whole process starts again.
That way the diver re breathes the same gas over and over again. The only remaining problem is oxygen. Every time the diver inhales, he inhales oxygen rich gas, his body metabolises the oxygen and then exhales oxygen poor, carbon dioxide rich gas. Therefore, oxygen must be added in the circuit at some point of the process. The way this oxygen is added is the fundamental difference between the 3 types of rebreathers.

SCR, CCR, mCCR, eCCR, Semi Closed and Closed Circuit Rebreathers - what does all that mean ?

As previously explained, the fundamental difference between the various types of rebreathers is how they manage the lack of oxygen in the filtered gas.

SCR (Semi Closed Rebreather): The system is composed of a nitrox cylinder, a constant flow injector, a loop, a scrubber, an exhale counter lung, an inhale counter lung, and an overpressure relief valve.

Every time the diver exhales, he exhales in the exhale counter lung, and every time he inhales, he inhales from the inhale counter lung then "sucks" the gas from the exhale counter lung through the scrubber. The whole principle of the system is the constant flow injection and the overpressure relief valve. As soon as the gas volume in the loop is too high due to the constant Nitrox injection in the system, the excess gas is vented through the overpressure relief valve and the gas in the loop is permanently renewed. As you now understand, these units are quite wasteful and are not completely bubbleless, and offer a lot less bottom time than fully closed rebreathers. With the new generation of closed circuit rebreathers, SCR units are getting less and less attractive and are slowly disappearing to the benefit of CCRs (Closed Circuit Rebreathers).

Oxygen Rebreather : The most simple type of closed circuit rebreather, but limited to 6 metres' depth (maximum depth at which you can safely breathe pure oxygen).

The system is simply composed of an oxygen tank, a loop, a counter lung, a scrubber, an overpressure relief valve and a manual diluent injector. As the diver goes deeper or metabolises oxygen, he (or the ADV) injects oxygen into the system in order to have enough gas to fill his lungs; as the diver goes up, the excess of gas in the circuit is vented through the overpressure relief valve (this principle applies to all types of rebreathers). Practically, the diver is only limited by his oxygen exposure. These units are mainly used in commercial and military diving due to their limitation in depth.

CCR (Closed Circuit Rebreather) : Contrary to the Semi Closed Circuit Rebreather, these systems do not let any gas escape when the diver exhales. The system is composed of a loop, a scrubber, an exhale counter lung, an inhale counter lung, an ADV (automatic diluent valve) and/or a manual diluent injector and a head. Two cylinders are connected to the circuit, one diluent tank (air, nitrox or trimix) to add gas as the pressure increases with depth, and a pure Oxygen tank to replace the oxygen the diver metabolised. The target of these units is to automatically (eCCR) or manually (mCCR) maintain a constant pp02 (partial pressure of Oxygen). To do so, the head is composed of multiple oxygen cells whose results are displayed on one or more handset to inform the diver of the oxygen content in the loop. The gas in contact with the cells is permanently analysed and as soon as the partial pressure of oxygen is lower than desired, some more oxygen is injected either by the diver (mCCR) or by the unit itself (eCCR). In the case of an eCCR, the result of the cells' analysis is interpreted by a computer that decides whether or not an oxygen injection is necessary. That way the diver can spend a massive amount of time underwater, practically limited only by the scrubber duration, the oxygen exposure, and his decompression obligations. A Rebreather like the Innerspace System Megalodon eCCR, with two full 3 litre tanks and a freshly packed scrubber provides over 6 hours in the water for the diver. As no gas escapes from the loop at depth, that time does not depend on depth (you do not use more gas when you go deeper), which makes these units very suitable for photography (silent and bubbleless) and technical diving.

LEARN MORE ABOUT SCR AND CCR TECHNOLOGIES HERE

Most Common Brands and Rebreathers currently available on the market:

Semi closed rebreathers

Dragger Dolphin : The Dragger Atlantis SCR Rebreather came onto the market around 1995 and was one of the first SCR’s available in large numbers on the open retail market (around 3000 units). An upgraded version was named the Dolphin and replaced the Atlantis around 1998. This unit comes with a harness, a box, and a wing style BCD system. The bailout tank and regulator have to be purchased separately. It is the most widespread semi closed rebreather, widely available for rental. Training is available from most agencies (PADI, TDI, ANDI, IANTD,...). Detailed Technical information can be found here. If you so desire, (even though we would not recommend it) TecEvolution would rent a unit for you and certify you as a Dolphin Semi Closed Rebreather Diver.

Closed Circuit Rebreathers

AP Diving Inspiration (ex Buddy Inspiration) and Evolution

The Inspiration classic is certainly the most widespread closed circuit rebreather in the world. Born in 1997, it was the first production closed circuit rebreather (as opposed to homemade). In 2005, it was replaced by Vision electronics Inspiration and Evolution, that have extra safety features, a single handset, lighter weight, and integrated trimix decompression software. Detailed information is available on TDI Evolution closed circuit rebreather course in Pattaya Thailand with TecEvolution, Pattaya's most evolved Rebreather dive centre.

Innerspace Systems Megalodon, the MEG

The Megalodon is a closed circuit rebreather used by technical divers worldwide. Probably the second most widespread unit in the World. Born in ??? it is a very robust, customisable unit. Its main advantages reside in its compact size, ability to use any size of tanks (ideal when traveling), Head Up pp02 Display (HUD), and high level reliability. Its main disadvantage is that it does not have any integrated decompression information (the new deco integrated APEX3 head is supposed to be out in the first quarter of 2007). Come and get certified megalodon diver and then dive with us ! TecEvolution is the only technical dive centre in Pattaya (of only two in Thailand) who owns two CCR units and will provide you a CCR Dive Buddy.

Ouroboros (2006)

The Ouroboros rebreather is a fully closed circuit, rear mounted counterlung unit. It is designed as an electronic control unit with full manual over ride. Advances in Co2 canister designs have been incorporated into the unit. A radial scrubber is accompanied by counterlungs and all other sensitive parts in a carbon kevlar case. Electronics finish the unit with a primary wrist mounted display, Head Up Display (HUD), a rear facing display and a completely redundant passive oxygen display showing true real time ppO2 independent of the main electronics. Its main advantages include a lot of warnings, integrated decompression (integrated VR3 computers), and rear mounted counterlungs that leave your chest free. Disadvantages include rear mounted counterlungs that prevent easy breathing in some positions, heavy weight and a high price (starting at 8250 GB Pounds). Learn more about Ouroboros rebreather here. Unfortunately, there is no ouroboros training available in Asia at this time (Dec 2006).

The most widespread mCCR : The Jetsam Technologies Ltd. mCCR KISS and KISS Sport

The Classic KISS is the original KISS rebreather. Most of the components for the Classic are individually machined so there has been only around 200 units produced. The Sport KISS is the newest KISS rebreather. It is a small, light weight rebreather which has been designed for recreational divers. Jetsam has been working on the Sport KISS for approximately two and a half years. They started to manufacture, assemble and ship this rebreather in 2006. This unit is the first viable CCR concurrent of SCRs for recreational divers. Unfortunately, there is no KISS training available in Pattaya, and no sport KISS training available in Thailand at this time (Dec 2006). Any Centre advertising a KISS rebreather course in Pattaya provides outdated information as the only available unit in town is NOT FUNCTIONAL anymore.