mouthpieces and mouthpiece valves

[crimediver]

I was also wondering about the CO2 buildup scenario that could result by removing one way valves. I suspect that could become a problem. All of my full face masks are equipped with an oral/nasal masks with one way valves for this reason with the exception od a Desco mask that is a free flow design. Just not sure how big a problem it would be.

[Bryan]

I agree that it is possible.....The original Aqua-Lung hose/mouthpiece assemblies did not have valves or cages in them and as far as I know, this was not an issue even when tested by the Navy.....I AM NOT an expert on this subject so don't take anything I say as an endorsement. It works for me but YOUR RESULTS MAY VARY....

[eskimo3883]

Hi,

Some of my paranoia comes from reading lots of post-mortems of deaths from technical diving. CO2 comes up in some of the accidents on the Andrea Doria and other deep wrecks. Essentials of Deeper Sport Diving (John Lippman) is really well written with many details on how to die underwater but many of the mechanisms are not really present at non-technical depths.

I have read quite a few older books published before and after valves entered mouth pieces and I have never come across anyone suggesting the addition of mouth piece valves would address CO2. I would think the Navy's evaluations would have shown up real issues after these guys saw a few miles. Less reading - more diving.




.

deaths in I read several books on deep diving accidents and several deaths ended up atrributed to CO2 just from strenuous excercise like fighting a current at depth. These folks were at very depths. I may just be reading too much.




descriptions on the basis of Very detaile book wit the best explainations on After 100 pages describing lots of bad things The depth , as the hoses are not quite the same as .

[Sea Explorer]

As far as I know the only reason for the one way valves is to assist in hose clearing. The volume of air in the hose is minimal relative to the volume of the lungs and the body only absorbs about 6% of the oxygen so the percent change is low in any given breath. The CO2 issue is a much bigger concern in a closed loop (rebreathers)

I have dove without mouthpiece valves on many occasions and for the longest time Spirotechnique produced a metal mouthpiece without one way valves. They even continued to do so after the invention of the aqua-stop mouthpiece. So there is 30+ years of diving at least without one way valves. Cousteau and company did lots of diving at extreme depths (300-400') without the one way valves. There are reasons for one way valves but CO2 has little to do with it. Just my thoughts. -Ryan

[luis]

I tested several mouthpieces with and without valves and here are readings using one of my Magnehelic (range: 0 to 3 inWC, smallest marking: 0.1 inWC, but easily readable to 0.05 inWC).

The vintage curved mouthpiece with my best silicon valves and vintage hoses (no regulator) had a breathing resistance from 0.25 inWC up to 0.5 inWC max (the max. was at maximum reasonable suction).

The new Mistral mouthpiece with vintage hoses (no regulator) had a breathing resistance from 0.15 inWC up to 0.2 inWC max (the max. was at maximum reasonable suction).

The curved mouthpiece without valves has an absolute max breathing resistance of 0.1 inWC. The low end during normal breathing is less than 0.05 inWC.

Any of the single hose mouthpieces I tried also had a maximum breathing resistance of 0.1 inWC. The low end during normal breathing is again less than 0.05 inWC.

My conclusion is again that the breathing resistance of the mouthpiece itself is insignificant compared to the mouthpiece valves. Anyone can double check this by just breathing through a mouthpiece without valves.

Another conclusion is that the breathing resistance of the mouthpiece valves in the new Mistral mouthpiece is minimal. The valves are actually very impressive. They almost feel like they are not there.

I hope to have the new Mistral mouthpiece set up to test with a Phoenix RAM at SD-IV, if anyone cares to try it. Talking about an eclectic regulator. I may play with adding some weights to the mouthpiece if needed.

[capn_tucker]

I'd be interested in trying your PRAM with Mistral mouthpiece. Have been thinking about doing the same to my PRAM, but decided to wait and see..

[luis]

I'd be interested in trying your PRAM with Mistral mouthpiece. Have been thinking about doing the same to my PRAM, but decided to wait and see..

I looked at the price of the new Mistral mouthpiece by itself and it was cheaper to buy a complete new Mistral (when the last of them were available) and use the mouthpiece. And, I ended up with a new Mistral/Titan first stage that I can use for a single hose regulator.

The second stage I will try it chest mounted this summer.

Aqua Lung is selling parts at retail price since it needs to hold on to them to provide long term support.

[Nemrod]

I have spoken with several rebreather sources but they simply are unfamiliar as you might guess about our needs. Does anyone know of a source for rebreather cages, valves and mouthpiece assembly.

I have BTW, contructed the PVC DSV but am not satisfied with several aspects of it, weight is one and flow is dimenished for whatever reason.

The rebreather stuff is terribly expensive to experiment with. They of course use a rotary valve to close the mouthpiece but I am wanting to close the inhalation hose while surface swimming or switching off to my secondary.

I haven't much time for this now but there must be a larger cage and valve we could locate for reasonable price.

James

[luis]

At the Boston Sea Rovers convention a week ago, I talked to three manufacturers/ distributors of re-breathers. I was asking about hose weights and mouthpieces.

The three companies that I talked to basically would not sell mouthpieces separately. One company (Dive Rite) said that if purchased as a replacement part they would require the old mouthpiece returned for evaluation.

I got the impression that they are very concern about do-it-yourself re-breathers using their components. It is a shame from our stand point, but they are concern about liability from the DIY re-breathers.


Two of the three re-breathers I saw do not use hose weights and I didn’t have to much time to talk to the third guy from SDS (Silent Diving Systems).

I hate to even have to think about hose weight, but if I want to tinker with the new Mistral mouthpiece, I think that weights will make it much more comfortable.

Let me add that the vintage curved mouthpiece in my opinion is much more compact and aesthetically pleasing that the new Mistral mouthpiece, therefore I will probably continue to use my curved mouthpiece most of the time even if it doesn’t perform as well. Yes, looks are important even to an engineer.

It would still be good to come up with a compact mouthpiece, with good performing valves, and a replaceable mouthpiece bite. A shut off would also be nice. Some of the re-breather mouthpieces (like the Dive Rite) looked really nice.