Produce air at depth

[rakkis]

... it would be pretty hard to find a reaction that produces breathable air. Several reactions evolve O2, but not many evolve 21% O2 and 79% some other breathable gas.

A point many people forget every 2 months when this discussion comes up again. Even if you had a small perfect artificial gill that extracts O2 from the water around you, you would not be able to breathe from it unless you were fairly shallow.

NOW... if someone where to make it so that it would exchange this O2 and CO2 directly with your blood supply... now we're talking. Sign me up!

Unlimited BT, no deco. Oh my! <swoons>

 

[Air On]

US Navy subs have systems off their sea chest (sea water inlet) that separates out fresh water and breathable air. Only thing that limits them staying under anymore, fresh food supplies.

I don't think your likely to see this for civilians any time soon. I don't know if they have it small enough for a personal dive unit either. Its been around for some time though.

One possible way?...
add electrical current from the reactor, salt enhances electric current in water...
You get pure "O" and pure "H" bubbles off the contacts...
If you add the gasses back together they burn and you get usable power and fresh pure water (H2O) as exhaust (alternative fuel).

If save the "O" and add other trace gas to dope it down you make breathable air (like nitrox?)

 

[hokie_diver]

New-ish subs do indeed have an electrolysis plant but it is an item regarded as somewhat dangerous and is not used on some boats. Oxygen candles are used instead, and there is onboard O2 storage as well.

 

[mikerault]

The O2 candles are used at standard temp pressure, use underwater can cause an explosion if water gets into the canister (see recent news reports about the Brit sub fatalities as a result of these candles). I have used them and worn them before when I was in the Navy. Another consideration is it produces Oxygen not Air, a depth Oxygen can kill you in pure form...

Mike

Mike

 

[SparticleBrane]

We breath in 21% O2, our body only uses about 7% we exhale 14%, the rebreath's 02 canister adds oxygen to bring the levels back to 21%.......

I was under the impression that with a rebreather (at least with CCR) you get to set the partial pressure of O2 you breathe either electronically (eCCR) or manually (mCCR). I believe with an SCR it's dependent upon gas mix and depth.
Note: I am not a rebreather diver, so take that for what it's worth.

 

[Thalassamania]

hi all,

firstly excuse my ignorance, im a very inexperienced diver as far as Scuba is concerned. But I have taken great liking to the sport and have read pretty much all the non fictional books for diving available out there. it seems that running out of air is one of the most common factors in diving accidents, especially in tech diving. I was wondering how comes noone has invented a device that through a chemical process creates breathable air at demand.

i know it sounds a bit off the wall but let me explain.

as we all know the problem with our tanks is compresssion-size-depth, i.e the deeper you go, higher pressure will make available air in your tank shrink, sort of speak. however if you were able lets say to produce air at depth, from a solid substance (via chemical rection) then the problem kind of disappears doesnt it. there are oxygen candles used in submarines and rebreathers that can produce oxygen via chemical reaction, if you could somehow produce nitrogen or helium (for trimix divers) from a solid form substance then you could address one of the most basic problems of a scuba diver. The great part is given that a solid substance wont compress due to depth, you will always be guaranteed a certain amount of air been produced at any depth. (I think !!!!) so for example if you activated your solid substance ponny at 50m it would produce lets say 300 breaths of air, given that you didnt dive any deeper than 50m and it would still produce the same 300 breaths if you activated it at 100m.

i know i make everything sound easy whilst it isnt. so not to give the wrong impression this thread is more about debating a concept rather than trying to pitch a product

You're missing the basic physics, the storage form is irrelevant, once it is changed to gas it is compressed to ambient and depth effects come into play. It will not produce the same breaths at 300m at it would at 100m.

Oxygen Candles? I don't think so. A candle uses a flame, and we all know from basic science, that a flame uses up oxygen. So even if the chemical of the candle produced oxygen, it would be burned up as soon as it neared the flame. Moreover, the flame would probablly grow large VERY quickly untill a nice explosion ended the entire process.

Oxygen candles (a bit of a missnomer) are very real and standard equipment. They're rather hot, about 600 degrees and about two kilos per person is needed for a day's oxygen supply.

 

[james croft]

Probably easier to not run out of gas when diving than to generate gas once you have run out. In fact, I'm pretty sure of it.

I wonder if they make an O2 candle in the 1.7 cubic foot size?

 

[lamont]

Actually, the chemical reaction in a rebreather basically converts the CO2 into heat and water.

I'd say a rebreather traps CO2 (gas) as calcium carbonate (solid) and water (still oversimplified though).

 

[Thalassamania]

Here's how oxygen candles work: They are a mixture of sodium, potassium, or lithium chlorate or perchlorate and powdered iron. Once lit the iron burns to iron oxide and thermal decomposition produces the appropriate chloride and free oxygen.

 

[Luis H]

Actually, the chemical reaction in a rebreather basically converts the CO2 into heat and water. All the O2 used by the reabreather diver is brought to the dive in a cylinder.

For a given dive, the rebreather diver carries a much smaller gas supply than an open-circuit SCUBA diver because 'all' of the O2 is available to the diver, whereas an open-circuit diver exhales large amounts of O2 into the water.

Does that make sense?

Let me try it this way...

When an open-circuit SCUBA diver inhales he takes in O2, but he only metabolizes a small fraction of that O2. The rest of the O2 is exhaled into the water, never to be seen again... The deeper the dive, the more O2 is wasted.

Since a rebreather is a closed* system the exhaled O2 is held in the system, and available to the diver the next time he inhales. The O2 cylinder is used to replace the O2 that has been metabolized.

*I'm trying to simplify this discussion by intentionally ignoring semi-closed rebreathers, gas venting on ascent, etc.

My understanding is that the Russian military re-breathers do use a catalyst that breaks CO2 into O2 and C. What I recall reading is that the chemical reaction can cause a huge amount of heat and can become very unstable very easily. It is the same scrubber chemical that caused the (or at least one) fire in the MIR space station.

I have seen an outfit trying to sell Russian re-breathers to the west and it always mentioned that the scrubber can be adapted and (I think) an O2 cylinder also neede to be added.