There are three new GEM Recreational Rebreather Instructors!

[Dr. Doug Ebersole]

Kim Smith and the whole team at Jetsam should be commended for bringing a great new recreational rebreather to the market!!!

You can see from the photos below that this looks very similar to open circuit scuba. It connects to a regular nitrox cylinder and uses your own open circuit regulator. However it has rebreather hoses and a scrubber like a conventional rebreather. This combination allows for the rebreather advantages of minimal bubbles, warm moist air, and gas extension (approximately three times longer than open circuit) but a much lower cost, easier training, and much lower weight for travel. The lower weight for travel and the minimal bubbles are especially attractive for underwater photographers like me.

After last week in Miami with IANTD's Tom Mount, there are now three new KISS GEM Instructors -- Doug Ebersole (Florida), Hayna Amnon (Israel), and Masayoshi Kondo (Japan). Here are a couple of photos of the three of us in Tom's pool last week.

Congratulations also to Susan Dasher of Dive Tech, Grand Cayman who also just completed her instructor course with Steve Tippets, also of Dive Tech.



Doug

 

[TSandM]

Doug, if you had somebody who was nibbling on the idea of rebreathers, but wasn't certain, is this a good entry option? (Not ME, mind you -- really.)

 

[Peter Guy]

Doug -- I stopped by the booth today and talked with someone about the GEM but one thing had me confused (well, one thing at the moment). He said -- "Say you dive it with a 36% mix -- you'd be breathing around 30%..." Huh?

I'll freely admit I don't know much about SCRs (let along CCRs) but what mix would you "normally" have in your bottle? As I understand this, the primary benefit is that you would extend your BT by about 3X -- but you don't get the PPO2/NDL advantage of CCR, is that correct?

So what is the "sweet point" of an SCR?

 

[Mr.X]

Congrats! You'll have to take some interior and exterior shots of the units for us! Curious to see how this new units works.

Cheers,

X

 

[gsk3]

Doug -- I stopped by the booth today and talked with someone about the GEM but one thing had me confused (well, one thing at the moment). He said -- "Say you dive it with a 36% mix -- you'd be breathing around 30%..." Huh?

Peter -

I think the point is that since you're recycling your exhaled gas, it drops in %O2. For instance, first breath on the unit you breath in 36%. Some of that O2 is metabolized to CO2. So the gas you breathout has lower than 36% O2. A quarter of the gas you breathed out gets exhausted as bubbles, and the other three quarters gets recycled through the scrubber to clean out the CO2, some 36% Nitrox from the tank is added back to the loop, and then the mix gets breathed back in. Assuming what you breath out is say 32% O2, the mix in the second breath will be something like: .25*32+.75*36=35% O2. Given steady and typical consumption, this reaches a steady state at around 4% lower than what's in the tank.
Since there's no O2 added like in a CC2, the %O2 in the loop will always be lower than the %O2 in the tank.

I don't dive rebreathers; this is just from what I've read.

 

[Peter Guy]

gsk -- Thanks -- that was my understanding. HOWEVER, is it possible to really know what O2 % you are actually breathing? While it may not be that big of a deal, I was just wondering? So planning the Decompression status (N2 loading) is sort of a "guess and by golly?"

 

[gsk3]

gsk -- Thanks -- that was my understanding. HOWEVER, is it possible to really know what O2 % you are actually breathing? While it may not be that big of a deal, I was just wondering? So planning the Decompression status (N2 loading) is sort of a "guess and by golly?"

From a discussion on TDS, it sounds like the GEM has a single O2 cell. So you do have a readout on your PPO2, just not a super reliable one.

 

[Rainer]

There's an O2 cell.

 

[ScubaSam]

Congratulations to you and your class mates on your certification.

At BTS, I drooled over the GEM in the KISS booth as its creator briefly explained how it worked. Of course most of it went over my head but interesting nonetheless.

 

[Dr. Doug Ebersole]

The GEM is a "passive" semi-closed rebreather, not an "active" SCR like the Drager Dolphin or the Azimuth. The rebreather allows escape of a fraction of each breath into the water column and the subsequent inhalation causes the addition of a small amount of gas to compensate for what is lost. It is basically gas-efficient nitrox. The ratio on the mouthpiece is 3:1 so you will get about three times as much time on your cylinder as you would on open circuit. It is recommended as a recreational rebreather with a depth limit of 132 fsw. It is recommended that you use 32-36% nitrox in the cylinder, understanding that with the recirculation you will actually be breathing about 4-6% less than this fraction of oxygen. As I mentioned above, along with the gas extension you also have the advantages of minimal bubbles and breathing warm moist air.

The setup is a standard nitrox cylinder (of any size) with an included Zeagle Express Tech BC. You can use any open circuit regulator and simply remove the alternate air source. In its place you attach the hose that connects to the t-piece which is an Aqualung Micron regulator that acts as a gas addition. The loop then has front mounted counterlungs at the level of the clavicles that clip onto the Express Tech and an Extend Air cartridge as a scrubber. There is a single oxygen sensor which is an "R22D". The unit comes with either a single Jetsam display, a Fischer connector and special Shearwater SCR computer (which is upgradeable), or with just a Fischer connector that you can connect to a Shearwater computer if you already have one.

The 2nd stage of your regulator goes around your neck on a necklace and acts as your bailout or to donate to a buddy in need. Should you have a problem with the unit, you simply turn off the DSV, take it out of your mouth, and go to your regulator's usual 2nd stage. You are then diving standard open circuit nitrox.

Hope this helps. And, yes, the hoses seem long. However, the company is aware of this and likes them for the breathing characteristics and the freedom of motion of your head.