Produce air at depth

[ctsibos]

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

 

[Walter]

Rebreathers are sometimes used. They do not manufacture air, but do convert CO2 into C and O2 through a chemical reaction. There is a limit to the effectiveness of a given volume of media ans a limit to how much media a diver can carry, so it does not produce an endless supply of breathing gas.

A gill that can remove disolved O2 from the water would be ideal. Don't look for it any time soon and I doubt it would be a DIY project.

 

[timle]

A cylinder holds the same volume of air at the same pressure (minus cooling) at any depth as the cylinder is a rigid body and isn't compressible. The problem with scuba and depth is in our lungs. The first stage and second stage in a regulator work together to produce air that is at the same pressure as the surrounding environment - as they work at the surface.

However this has a drawback - if I fill the same volume (my lungs) at the surface (1 ATM) then I fill my lungs at 33 feet (2 ATM) I will have twice as many molecules in my lungs. Hence every breath at 33 feet is like 2 on the surface. Unforunately the CO2 builds up in my body just as fast and I need to breath at the same rate regardless of depth (or increased due to nerves, narcosis, working too hard, etc) and hence my air goes twice as fast, or three times as fast at 66, or four times at 100, etc.

 

[ekremer]

There have been several attempts at a gill system, the most resent I saw was by an Israely company and it was in a popular science (mechanic?) about a year or so ago.
here is a quick link
http://www.defensetech.org/archives/001938.html

 

[fppf]

The biggest problem with scuba is not gas supply.
Its trying to figure out how to get O2 into the body and the CO2 out of the body, without any other inert gasses.

They have tested and made liquid breathing systems for years (IE the Abyss). The problem there having is not getting O2 into the body, its getting the CO2 out.
But just imagine, if they got it to work you could dive without getting Narced or have to worry about Deco.

 

[O2BBubbleFree]

Rebreathers are sometimes used. They do not manufacture air, but do convert CO2 into C and O2 through a chemical reaction.

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.

 

[acelockco]

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.

 

[kamfan]

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.

You might want to check this out.

http://en.wikipedia.org/wiki/Chemical_oxygen_generator

 

[Firediver]

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%.......

 

[jefffalcone]

Aside for all of the other problems with this idea, the chemistry won't work. The added pressure would increase the activation energy of any reaction to the point that it would be difficult to make the reaction occur. If pressurized air could be produced by a simple reaction, given the cost of running compressors, we would probably fill our tanks at the surface this way. Also 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.