How much deco does 80% remove?

[Munin]

Am I the only person that has noticed that this guy is asking for practical advice on planning a deep air decompression dive in cold water with no deco training and absolutely no clue how to figure out the deco on his own and worse yet, that everyone here is answering his question?

Crispos, no offense, but get the proper training. If you're asking a question that basic you obviously have no business doing that dive.

What the??

 

[blacknet]

Munin once bubbled...
Am I the only person that has noticed that this guy is asking for practical advice on planning a deep air decompression dive in cold water with no deco training and absolutely no clue how to figure out the deco on his own and worse yet, that everyone here is answering his question?

Crispos, no offense, but get the proper training. If you're asking a question that basic you obviously have no business doing that dive.

What the??

Hello,

With the modern marvel called the internet it's easy for anyone to find the information they are looking for. Anyone can goto www.gap-software.com and download gap. Anyone can goto www.v-planner.com and download v-plan. Anyone can also STFW and learn all about decompression theory and practice. He/she did state certs to 50% so that tells me IANTD adv nitrox. I think you missed the boat on what he/she was asking.

Ed

 

[Cave Diver]

crispos once bubbled...
So far I have been trained in 50%, and yes, I kind of like the fact if the **** hits the fan, I can get up to 70 feet and use it. No buoyancy control is not a problem, I agree why breathe any N2 when you want to get rid of it. Also, could be used for a backup O2 unit in an emergency?

Perhaps I have a lingering fear that a smoker might walk over to my car or my tank and it might be leaking....I guess I figure the 80% is abit less combustible (probably not). and lo and behold, I was woken up last night at 4am, my (late night owl) roommate said my car was hissing, and it turns out somehow my big tank valve got slightly cracked open. I will analyse all this and improve my dive decision making. Thanks, again.

It's common for technical divers to carry multiple deco gasses.

Deep stops on back gas, switch to 50% at 70' then 100% at 20'.

Latest discussions I've seen are looking at the advantages of a 50/50 Heliox mix instead of a 50/50 Nitrox mix.

Yes, it can be used as a backup 02 bottle in an emergency.

O2 is NOT flammable. It merely accelerates (greatly) a combustion process. There has to be other factors involved, and I seriously doubt that a smoker near your car where an 02 bottle was leaking would pose a significant hazard.

If they got close enough, the cigarette might burn faster, but the chances of some sort of an explosion seem pretty far fetched.

Someone please correct me if I'm wrong.

 

[Rick Murchison]

sheck33 once bubbled...
The number one reason given by divers i have seen use 80/20 was 'it gives you a larger margin of error in bouyancy control' They are obviously 'afraid' of 100% O2. It gives them more room to play with (read: screw up) at the 20ft stop
They use 80/20 to compensate for bad bouyancy control.

this is not my conclusion btw, they TOLD me this

and why use a deco gas on the 20ft stop with any nitrogen at all? its the N2 you want to get rid off in the first place.

I have never heard any diver say they used 80/20 as a crutch for poor buoyancy. Zero. As in none. As far as I can tell this is a complete myth dreamed up by the "80/20 is stroke mix" crowd.
But prove me wrong. Put some names to the claim.
Rick

 

[sheck33]

Rick Murchison once bubbled...

I have never heard any diver say they used 80/20 as a crutch for poor buoyancy. Zero. As in none. As far as I can tell this is a complete myth dreamed up by the "80/20 is stroke mix" crowd.
But prove me wrong. Put some names to the claim.
Rick

I can assure you that that is the thing these divers told me, i am just repeating what they said. But i am not going to put their names on the board here.

hell, they can breath pure hydrogen for all i care

 

[Rick Murchison]

Cave Diver once bubbled...
O2 is NOT flammable. It merely accelerates (greatly) a combustion process.

... Uncle Ricky climbs onto soapbox...
I don't know where this dangerous and misleading hair splitting statement got its origin, or why it keeps its life, but the facts are:
Practically nothing is "flammable" by itself. The ingredients for a classic fire are enough heat for ignition, fuel and oxygen. Whether you call the fuel flammable and the oxygen the accelerator or the other way around is irrelevant. Pure oxygen will cause fire where no fire would be without it, as will adding fuel to a pure oxygen environment. You get the same BOOM regardless of your definition.
If you intend to handle rich mixes, and especially if you plan to mix them yourself, please get (at a minimum) a copy of Vance Harlow's Oxygen Hacker's Companion and read it cover-to-cover before proceding.
Better yet, if you can get your hands on the old Navy training film "The Man From LOX" do so and watch it.
If I sound a bit harsh in my criticism of the common knowledge that "O2 is not flammable" it is intentional. Oxygen is not to be trifled with - it is dangerous in the exterme - it can cause fires you can't extinguish, or deadly explosions. It can be used safely, and should be used by any serious technical diver. But you absolutely must know what you're dealing with or sooner or later it will bite you.
Rick

 

[sheck33]

Rick Murchison once bubbled...

... Uncle Ricky climbs onto soapbox...
I don't know where this dangerous and misleading hair splitting statement got its origin, or why it keeps its life, but the facts are:
Practically nothing is "flammable" by itself. The ingredients for a classic fire are enough heat for ignition, fuel and oxygen. Whether you call the fuel flammable and the oxygen the accelerator or the other way around is irrelevant. Pure oxygen will cause fire where no fire would be without it, as will adding fuel to a pure oxygen environment. You get the same BOOM regardless of your definition.
If you intend to handle rich mixes, and especially if you plan to mix them yourself, please get (at a minimum) a copy of Vance Harlow's Oxygen Hacker's Companion and read it cover-to-cover before proceding.
Better yet, if you can get your hands on the old Navy training film "The Man From LOX" do so and watch it.
If I sound a bit harsh in my criticism of the common knowledge that "O2 is not flammable" it is intentional. Oxygen is not to be trifled with - it is dangerous in the exterme - it can cause fires you can't extinguish, or deadly explosions. It can be used safely, and should be used by any serious technical diver. But you absolutely must know what you're dealing with or sooner or later it will bite you.
Rick

Rick, you are totally correct in stating that gasses containing high O2 concentrations should be handled with care. You already state almost nothing by itself will burn which is true but your statement then:

'Whether you call the fuel flammable and the oxygen the accelerator or the other way around is irrelevant'

is wrong, O2 IS NOT flammable it IS the accelerator and by definition the fuel is the flammable stuff. Of course you get the same boom regardless of definition BUT saying that O2 is flammable is simply wrong. Now for example hydrogen IS flammable and argon is not. But you can not call hydrogen an accelerator.....

yea, all hearsplitting stuff but the field of physics taught me to do that....ut:

 

[Dr Deco]

Dear Scuba Board Readers:

Oxygen and Fire

As Rick related above, it is a bit misleading to argue about oxygen and flammability. It is true that oxygen in oxygen will not burn, but anything else in oxygen will burn, often ferociously. NASA considers that 28% oxygen in a balance of nitrogen is the point where the mix acts as if it were pure oxygen. This is surprising to most. Nitrogen is more than a diluent. It is a quencher of free radicals by which fire propagates. When the concentration of free radical scavengers becomes too low, the reaction proceeds very fast, even if the oxygen molecules are in the minority.

Thus escaping oxygen in an auto trunk or backseat could cause considerable problems. Metal will burn (oxidize) in oxygen as if it were wood. It is frightening to behold.

Dr Deco :doctor:

Please note the next class in Decompression Physiology :grad:
http://wrigley.usc.edu/hyperbaric/advdeco.htm

 

[blacknet]

Dr Deco once bubbled...
Dear Scuba Board Readers:

Oxygen and Fire
Thus escaping oxygen in an auto trunk or backseat could cause considerable problems. Metal will burn (oxidize) in oxygen as if it were wood. It is frightening to behold.

Hello,

Ah yea clarity at last, as with what Rick posted. This very same reason is why all the big names use the 26.5% rule and say the 40% rule is BS. However I do not want this thread hijacked into a debate of rules.

One thing that has yet to be mentioned is the decreased material lifetime in high O2 rich environments.

Ed

 

[crispos]

Yes, Munin, you are partially right. Good point. You have to be careful who you give advice to. But I am very cautious compared to the number of yahoo old timers I have heard go to plus 200 on air before they were trained properly too. I started diving doubles three years ago.

Actually, it has been hard finding a tech instructor in Toronto. Alot of them don't market and therefore you only get one on one courses or worse, they are not insured, or don't live in Toronto due to high cost so logistics are tough. I've been trying to locate a decent instructor since I got back from Europe over a year ago. By the way, in Europe, they go down to 50 metres without much ballyhoo about it. I am IANTD Adv Nitrox and an ex-chemist so I know abit about gases. Watch that cigarette.