Why no poor man's rebreather?

[kidspot]

Why has not someone invented a cheap, safe, easy to use semi-rebreathing system?
Since we only use 4% of the 21% O2 available in a breath from an open circuit tank, why is there not a system that would allow us to rebreath that first breath twice before expelling it thus allowing double bottom times or much smaller air tanks? Is it that difficult to scrub that one breath of CO2? Does that one breath really have to be scrubbed? If you start with Nitrox you should have about 30% O2 in the first exhaled breath to play with and only have to deal with CO2. Even if you could only save half of that first breath it could be a great advantage in diving with less bubbles, smaller tanks, longer bottom times, less dry mouth, deeper with nitrox, etc. Scuba has been around 60-70 years and has changed very little in the basic system.
This may have already been answered but I have not found it on this forum.
Don't flame me to bad......

One attempt at this is the Apocalypse rebreather which is slated for shipping shortly (it's been delayed since February) Full price is $2995- which, while still quite high, is closer to being affordable. Perhaps a step in the right direction ... still have to wait and see when it is released. Rated for dives to 260fsw Open Safety Equipment

The Mark VI Discovery was recently released as a recreational unit for $6468 -it's as much as a number of other units on the market.

btw - both are full CCR's, so as pointed out above, if you are interested in a less expensive route, consider a used Dolphin or similar - they can be found for around $1500 (I've known a couple of dive shops that had them sitting in a corner collecting dust and were quite happy to sell them)

Whatever route you end up going, there is still training which will run $1-$1.5k as well as travel expenses if you don't have a local instructor.

Still it does look like the days of entry rebreathers costing $12k may be over ...

Aloha, Tim

 

[Rhone Man]

That is a pretty big step. For me, price is only half the issue. The other is safety record:

http://www.scubaboard.com/forums/rebreathers/243450-900-times-more-deadly-than-oc.html

 

[kidspot]

That is a pretty big step. For me, price is only half the issue. The other is safety record:

http://www.scubaboard.com/forums/rebreathers/243450-900-times-more-deadly-than-oc.html

yup - definitely a serious consideration.

Interesting that this safety report was compiled by the same folks who designed the Apocalypse rebreather ... around that safety report ... hopefully they will suceed in the safety aspect of their project.

Aloha, Tim

 

[ScubaRich]

Here it is, cheaper than just a tank:

A $100 HOT WATER BOTTLE PENDULUM REBREATHER

 

[diver 85]

You may not feel that way if you knew who that is. He is a well know rebreather expert and designer with a bunch of patents to prove it. Real nice guy to and yes that is a working rebreather.

but look how many ugly sticks he's been beat with--certainly that has to count for something.....

 

[Tienuts]

yup - definitely a serious consideration.

Interesting that this safety report was compiled by the same folks who designed the Apocalypse rebreather ... around that safety report ... hopefully they will suceed in the safety aspect of their project.

Aloha, Tim

Mark my words - the Apoc will end up being a disaster. There is too much control removed from the diver, and placed in the hands of the CCR itself. The reason mCCR has a better safety record than eCCR is the computer between your ears is better at figuring trouble out than the one in the head of your CCR. As someone before me said - If you engineer a device to be idiot-proof, all you have done is engineered bigger idiots.

But this is not why the Apoc will kill more divers than the YBOD could ever dream to. You know why we will never have flying cars? Cause most people can't drive, much less fly. As it stands now, most people can hardly dive OC, much less CCR. To make a more affordable CCR, and put it in more hands, just statistically increases the amount of potential fatalities.

Tony

 

[smellzlikefish]

I think I'm about to switch to longer snorkels.

 

[padiscubapro]

Semi closed allow you to do that sort of. Remember 4%x2 from the 21% puts you realy hypoxic and ready to have the walls close in on your brain...not a good time.

".

I am shocked that a supposedly CCR certified diver can make such an incorrect statement.. We exhale 4% co2 by volume, but on any rebreather this 4% is scrubbed out.. What we get is a slight reduction in volume since some of the o2 was consumed.. this is a time based thing.. You don't loose 4% o2 ever breath..

lets use a simple example (no o2 added).. lets say we have a dive to 33 fsw (2 atas), lets assume a reasonable loop displacement volume of 6l, this means that we have 12l of gas in the loop.. if we ony used 21% that means we have 2.52l of gas.. if we metabolized 1l of gas per minute (a reasonable assumption), we are down to 1.52l of gas, and our volume is now down to 11l.. so the fo2= 1.52/11 = 13.8% (not good for the surface) but perfectly ok for 33fsw po2=.276.. An average person swiming, probably takes 10-15 breaths per minute.. cut this in half (by time)and you still have a breathable mix at the surface.. certainly not 2 breaths....

 

[sea2summit]

I am shocked that a supposedly CCR certified diver can make such an incorrect statement.. We exhale 4% co2 by volume, but on any rebreather this 4% is scrubbed out.. What we get is a slight reduction in volume since some of the o2 was consumed.. this is a time based thing.. You don't loose 4% o2 ever breath..

lets use a simple example (no o2 added).. lets say we have a dive to 33 fsw (2 atas), lets assume a reasonable loop displacement volume of 6l, this means that we have 12l of gas in the loop.. if we ony used 21% that means we have 2.52l of gas.. if we metabolized 1l of gas per minute (a reasonable assumption), we are down to 1.52l of gas, and our volume is now down to 11l.. so the fo2= 1.52/11 = 13.8% (not good for the surface) but perfectly ok for 33fsw po2=.276.. An average person swiming, probably takes 10-15 breaths per minute.. cut this in half (by time)and you still have a breathable mix at the surface.. certainly not 2 breaths....

Perhaps I was trying to be nice to the OP and answer his question in a way easy to comprehend? We can use your logic (which is completely sound) and mathmatically argue that as long as we decend fast enough never have to add O2 either but that wouldn't answer his question.

 

[Couv]

Why has not someone invented a cheap, safe, easy to use semi-rebreathing system?......

The re-cycle breath one time idea is not new, see this post by Luis H in an answer to an April Fool's day post I made in 2008.

http://www.scubaboard.com/forums/3471543-post6.html

For plans on making a cheap rebreather, here's one for $3.00
Project021017ThreeDollarRebreather


couv