Question CCR for recreational depths

[inquis]

so you add another baggie (and another 100 molecules of oxygen). Now you suddenly have 200 molecules of oxygen.

Got it, so you were talking about different PO2s. Certainly density changes then.

 

[Angelo Farina]

Example:
On the surface you have a one gallon baggie of gas with exactly 100 molecules of oxygen in it. We all know that at 33' (one atmosphere deeper than surface) the volume of gas will be halfed by the pressure. Thus you will have same amount of gas in the baggie but it will take up half the area. To have the same area taken up you would have to double what you stated with so you add another baggie (and another 100 molecules of oxygen). Now you suddenly have 200 molecules of oxygen. Extremely simplified and I know someone will criticize my terminoligy.

Almost correct, but what halves is volume, not area...

 

[lexvil]

So this is a curiosity question. I had the chance to use a R1 O2 rebreather the other day in a try it dive at local pool. It was a pretty cool experience and it prompted a question. Would one of these rebreathers be able to replace my conventional OC scuba for diving at recreational depths?

Here is my situation. I typically dive with a steel 120 and most if not all my diving is above 100'. I am getting older and father time is catching up with my back. at some point I will no longer be able to sling all the lead and steel. The CCR is much lighter than a traditional OC system.

I understand that because of the PPO of a pure O2 diving is limited to 20' and repeated prolonged O2 can have an effect on your lungs. But I heard from the guy doing the try it dive that the rigs can be modified to use air as a diliuant and work at greater depths.

My question is would this be a viable option? With an upgraded DR1 would it be a viable way to dive within recreational limits? With a system like this would it a kin to breathing Nitrox at a fixed ratio or would it would the gas blend be adjustable like used in other CCRs? This is mostly an academic exercise, but I would not mind being able to go out on my usual underwater bumbles, which normally range from 30-60 FSW without having tank pressure as my limiting factor.

I assume the subsequent pages (more to come I bet) should answer you question

no.

a few years back I thought Hollis was on the right track with a fairly simple nitrox based unit (Explorer?) they were working through the issues when HUISH bought them and it was the first thing to go. Overall for the shallow stuff there are far simpler options, like air.

 

[Wibble]

And now there's the Mares Horizon (Revo-inspired) SCR.

Most of the complexities of rebreathers without the full benefits. They're slightly more simple than a CCR rebreather to dive but there are very few concrete reasons for diving one of these rather than a CCR. They are slightly less expensive than a CCR. The most valid case I've seen is diving in locations where high pressure oxygen isn't available, for example getting fills from membrane compressors.

 

[The Chairman]

I suppose that's true, and there's the actual explanation why pure O2 CCRs are not very useful outside of niche applications.

Any CCR can be converted to pure O_[2 by turning the ADV off and doing an O_[2 flush.

 

[broncobowsher]

Any CCR can be converted to pure O_[2 by turning the ADV off and doing an O_[2 flush.

Or put an O2 bottle on the DIL side as well.

 

[The Chairman]

This risk would be mitigated by any of the constant O2 mass flow solutions out there (mCCR etc.).

Or setting your PPO_[2 to anything less than 1, like 0.7.

Or put an O2 bottle on the DIL side as well.

Why? When I am less than 20FSW, I always switch to pure O_[2. I do have to manually add O_[2 every now and then so I can breathe easily. Start the dive on dil and end it on O_[2. I do want to go to Venice Beach, FL and use my SF1 to look for sharks teeth. I doubt I'll ever switch my adv on. I'll still need dil from time to time, but not often.

 

[broncobowsher]

Or setting your PPO_[2 to anything less than 1, like 0.7.

Why? When I am less than 20FSW, I always switch to pure O_[2. I do have to manually add O_[2 every now and then so I can breathe easily. Start the dive on dil and end it on O_[2. I do want to go to Venice Beach, FL and use my SF1 to look for sharks teeth. I doubt I'll ever switch my adv on. I'll still need dil from time to time, but not often.

In the context of a pure O2 rebreather out of a normal rebreather, the suggestion of O2 in the dil bottle...
The ADV will be functional. The wing will be functional. Everything will be as functional as it should be. Except you only have pure O2 and the matching depth restrictions. That would be a pure O2 rebreather out of a regular one.

 

[Wibble]

Don't forget your oxygen

 

[grantctobin]

Don't forget your oxygen

Ehhhhhh. More like take appropriate low PPO2 breaks.