Rebreather Diving

Many dive industry forecasters consider the future of diving to lie with rebreather technology. In the past, rebreathers have been associated with complex set up and maintenance procedures, being heavy and cumbersome, requiring technical level training and not being terribly reliable.

Now manufactures are beginning to produce a range of lighter weight, more reliable, easier to use and fool proof rebreathers. The first one to market is the Poseidon Mk VI Rebreather.

Last week, two of our intrepid instructors, Neal Sanders and Mike Waddington, from Davy Jones’ Locker completed try dives on Koh Tao with the new Poseidon Mk VI rebreather.

The Poseidon Mk VI is the first rebreather produced to meet the standards of PADI’s new Recreational Rebreather courses: PADI Rebreather and PADI Advanced Rebreather. Check out more info on this rebreather at All the major manufactures have recreational models launching in the next couple of years, so they can compete in the recreational market brought about by PADI’s new courses.

To qualify for a PADI recreational rebreather diving course the prerequisites are: a diver must be a minimum of Open Water qualified, Nitrox certified, over 18 and have completed a minimum of 25 dives. So no longer is it the realm of technical divers.

All of the set up procedures are now automated. Scrubber packing problems have now been eradicated, as there are replaceable scrubber cartridges. And all potential malfunctions are now clearly displayed to you on a head up display that also makes an audible beep and vibration alert to warn the diver of problems.

In the unlikely event of any problem the diver just switches from closed circuit to open circuit by flipping one lever on the mouth piece, and directly ascends t

o the surface, which should be possible from all recreational dives, as all recreational dives should be no decompression dives. The open circuit gas is supplied from the

diver’s dilutant gas in the rebreather. So there’s no need to carry extra bail out gas.

The unit we tried was fitted with two three litre tanks, a standard Halcyon 30lb wing/back plate and Poseidon regulators. It seemed light and comfortable, weighing about 18 kilograms. Putting the unit on a getting ready to dive was easy and took only a couple of minutes.

Once we were in the water we off! If you’ve never dived on a rebreather before, it will take you a bit of getting used to. You don’t control your buoyancy with your lungs as with standard open circuit. As the counter lungs inflate and deflate by the same amount your lungs inflate and deflate by as you breathe. All buoyancy control is done by varying the amount of gas in your wing and varying your trim. Our instructor told us it takes about 30 dives to get competent on the unit.

So why might rebreathers be the future? Well the first thing a diver notices is just how quiet you are when you are in the water. There is virtually no noise at all. This means you can get much closer to the marine life. Secondly, as you are recycling your gas and only using a small percentage of oxygen with each breath, at recreational

levels, you have virtually unlimited gas. Finally, a rebreather is constantly adjusting the partial pressure of oxygen in the breathing loop, so you are always breathing the ideal gas mix. In the Poseidon this means you are breathing a partial pressure of oxygen at 1.2 ata. This means you have very, very long no decompression times on recreational dives.

So far so good. So why are people not diving them regularly already? Well one issue has always been the technical aspect of the units. But this now seems to hav

e been fixed. These units are virtually idiot proof! Mike and I certainly thought so. The second issue has always been cost. At the moment this is still an issue. A new rebreather is going to cost about 250,000 Baht. Plus there are scrubber and sensor consumables which need replacing periodically.

Poseidon has tried to get around the purchasing of the units problem by producing a battery/memory cartridge that each user buys. This can be transferred from unit to unit. This cartridge carries all the divers’ information. So once the correct cartridge is fitted the rest of the unit essentially becomes like their own unit. Dive shops can then invest in the units and rent them to the divers.

The scrubber cartridges currently cost about 2000 Baht per cartridge and need to be changed every three hours; therefore working out at about 700 Baht per one hour dive.

This might seem expensive at the moment, but as more rebreathers come onto the market and more third party suppliers get involved in making the consumables these prices are going to come down significantly.

Another barrier has been; when a diver completes a rebreather course, he is only qualified to dive on the brand of rebreather which they qualified on. If they want to dive another brand of rebreather, they have to complete an entirely different course. PADI have gone some way to fixing this problem. The Poseidon re

breather course takes four to six days to complete depending on whether you do Rebreather or Advanced Rebreather. This qualifies you to dive on a Poseidon Mk VI. If in the future you want to dive a different brand, then you will only need to complete a one day crossover course. So I guess you could consider it like taking a Scuba Review each time you want to change brands.

So at the moment this is still new exciting but expensive territory, but could this be the future for diving? If you think so, perhaps it’s better to be an ear

ly adaptor to the new technology rather than chasing the crowd. After all, who would have thought 20 years ago we would all be diving regularly with Nitrox gas and dive computers the size of a watch on out wrists.

If you are interested in finding out more about rebreathers our technical department run rebreather courses on AP Valves’ Inspiration Rebreather. Contact for a try dive or just more information.

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