What's your PO2?

[Cave Diver]

A recent discussion in another thread highlighted the difference of opinions among divers on an acceptable PO2 for gas planning. Over the years, I've seen a shift in the recommended max PO2.

I'm a bit curious about the difference in personal attitudes and training on the limits that people use in planning the working portion and deco portion of their dives.

For working portion, do you normally prefer 1.0 or less, 1.2, 1.4, 1.6, or something else?

For the deco portion of your dives do you normally prefer to keep your PO2 at 1.4, 1.6, or something else?

What adjustments (if any) do you make for adverse conditions? (strong current, cold water, etc.)

What is the main driving force in your choices?

[Blackwood]

Right now? About .21.

Usually plan for <1.2 max working and ~1.6 max deco. I don't have a good answer for why I make those choices; it's what I was taught. I have not experimented, nor do I adjust based on conditions.

[Captain12Pk]

Bottom gas is usually planned at about 1.20.
Deco gas is planned at 1.60.

[Chris at Silent World]

Depends on depth and OC or CCR.

For OC dives up to 150' with no or 'light' deco - 1.5 max backgas and 1.6 deco

Deeper OC dives, 1.4 and 1.6

On CCR - 1.2 for NDL or light deco, 1.1 for deeper/longer dives

[Splitlip]

I'm in my fifties. Rec diver.

1.4.

I can dive every day, so I have no problem blowing off a dive.

Good thread.

[wedivebc]

1.4 bottom gas 1.6 deco on OC
1.0 dil, 1.3 setpoint, 1.6 bailout (if direct ascent possible) 1.6 deco bailout on CCR

[Jax]

Seems like a lot of people like the "1.4 PPO bottom, 1.6 PPO on deco". Is that because it's a fairly often used, well known set of parameters with which people are comfortable?


Are there any of you that does your loading calculations during the dive and deliberately choose your PPO according to the gradient? I know many advanced dive computers let you plug in your M-values.

[Kern]

OC, I use a max of 1.4 working, & 1.6 deco, for dives to 55mts; 1.3 working, & 1.6 deco, 55 down to 75mts; 1.2 working, & 1.6 deco, 75 to 90mts. Unless the wreck i'm diving is little more than a debris field, I usually average less than 1.2 to 1 for BT per dive.

I use these mainly for convenience, due to the mix's I use.

[Kern]

I use those PPO2 values in relation to the mix for a particular dive. It's to limit the effects of O2 & narcosis. Nothing at all to do with decompression. Besides, I'm a VPM person, I don't care about no "M" values.

[David_57]

1.4 bottom, 1.6 deco

[ScubaFeenD]

I used to be OK with 1.4 working gas and 1.6 max contingency.

Now I am more comfortable with 1.2-1.3 (favoring 1.2 or less) for working gas and 1.6 for deco as long as I am not going to be exerting myself on deco.

[Dr Wu]

1.4

1.6

[ScubaFeenD]

Are there any of you that does your loading calculations during the dive and deliberately choose your PPO according to the gradient?

I am not sure what you are asking here. Are you asking if people choose their pPO2 based on how far they want to drive the pressure gradient?

[Karen Cleveland]

For the working portion of the dive, we (my dive buddy and I) keep it at 1.0-1.2.

For the deco portion it is at 1.6.

On extremely long dives (4 hrs+ -cave) we run .8 or .9, because by the end of those dives the CNS is getting high....and we deco on O2 in this scenario.

For ocean diving, the 1.0-1.2 is in case of adverse conditions.

The main driving force is flexibility and CNS.

[peterbj7]

On open circuit 1.4/1.6, though I sometimes go above these limits. My rich deco gas is never richer than 80%. On closed circuit it depends on the length of the dive - for short dives (up to ca. 2hrs) 1.3 on the CCR, 1.6 on O/C deco, for long dives 1.1 or 1.2 on the CCR, again 1.6 for rich deco.

[Jax]

How did you choose those values?

[D_B]

I don't have enough dives to have any real experience but was taught 1.4 max, 1.6 contingency and to lower those if conditions are anything less than benign , like cold water, current, or just not feeling up to snuff
... Instructor noted that he's started using a max 1.2 for the dive portion

[kjvander]

1.2 bottom gas.....1.6 deco....1.2 as for being conservative as diving is mostly done in cold water with possible currents....

[peterbj7]

How did you choose those values?

Initially advice, then experience. I should say that when doing intensive back-to-back diving on CCR I tend to knock 0.1 off those values, just as a precaution. I've never so far had any oxygen problems.

[Kern]

I don't have O2 considerations on OW, single tank, NDL dives. It's very rare for my PPO2 to exceed 1 on such dives, & then only for a small amount of time.

[TSandM]

For a benign dive with little exertion, I'll go to 1.4. If I'm swimming steadily, especially if swimming hard, I prefer 1.2. Because I rarely go below 100 feet without helium, it isn't an issue.

1.6 for deco.

I base those decisions on the fact that there have been very, very few reported cases of toxing at or below 1.4.

[Chris at Silent World]

Seems like a lot of people like the "1.4 PPO bottom, 1.6 PPO on deco". Is that because it's a fairly often used, well known set of parameters with which people are comfortable?

Yes, 1.4 for 'working' and 1.6 for deco is the standard in tech diving. 1.6 is the baseline, above which most agree you are in unknown territory. Even though OxTox has been observed at 0.5ATA, so its not watertight.

IANTD teaches up to 1.5 for shorter/shallower stuff where exposure time is not an issue



Are there any of you that does your loading calculations during the dive and deliberately choose your PPO according to the gradient? I know many advanced dive computers let you plug in your M-values.

On a CCR you mean? You could only do this by gas switching on OC.

Anyway, on the rebreather the setpoint of PP02 is usually constant and often lower than on OC. I can make my ascent time lower if running in manual mode by increasing my average PPO2, but Ill never exceed 1.2 on the bottom and it only saves a few minutes here and there.

I dont know anyone that has a computer where they are adjusting the algorithm underwater by entering m-values.

[PfcAJ]

I'm a fan of 1.2-1.4ish (maybe less) for the bottom portion of the dive. This gives me enough wiggle room to go a bit deeper if need be, but a conservative enough ppo2 to up the deco gas % to accelerate the deco to a reasonable time.

DCS is fixable, toxing is not. I'd rather err on the side of conservative with regards to ppo2.

[Hollywoodivers]

1.4 to 1.6 for recreational . No Toxing please.

[ajduplessis]

Bottom gas PPO2 of 1.5 where there is a physical bottom (floor) for that depth
Bottom gas PPO2 of 1.4 where there is not a physical bottom (floor) for the MOD of the dive
Deco @ 1.6

Subtract 0.2 of the above mentioned PPO2 for cold and high workload dives, deco stays at 1.6

[Pullmyfinger]

1.4 and 1.6 for me. This is as I was trained, I'll stick to that. I live in a warm water area.
-Mitch

[vladimir]

.....

[DeepSeaExplorer]

For recreational dives with no deco, 1.6 on the bottom. 1.4 for deco dives.

[Tortuga68]

1.6 for deco

2.0 for bottom

[AndrewA]

On the rebreather 1.3.
On OC 1.4 max (but usually 1.2-1.3) with 1.6 for deco.

[Jax]

. . . You could only do this by gas switching on OC.

I dont know anyone that has a computer where they are adjusting the algorithm underwater by entering m-values.

Nothing underwater, Chris; the Sol tracks three bottles and their associated EAN mix.

[awap]

I'm still using 1.6 as long as the workload is light.

[muddiver]

On CCR I follow the ANDI recomendation of 1.3 on bottom.

The ANDI recomendation for OC is a max. of 1.45 for the dive and 1.6 for your bailout/deco cylinder.

[peterbj7]

Bottom gas PPO2 of 1.5 where there is a physical bottom (floor) for that depth
Bottom gas PPO2 of 1.4 where there is not a physical bottom (floor) for the MOD of the dive

Strange distinction. Don't you trust your buoyancy control?

[Cave Diver]

2.0 for bottom

That's a bit higher than the norm. Is this based on agency/training recommendations or personal risk assessment?

[Cave Diver]

Oooops! I just realized I never put mine in. :blush:

OC - recreational and light tech 1.4 working 1.6 deco

OC - deeper tech 1.2 planned, 1.4 max for contingency 1.6 deco

CCR - short duration (< 2 hours) 1.2 working, 1.6 deco, 1.4-1.6 bottom bailout.

CCR - long duration (2+ hours) 1.0 working, 1.6 deco, 1.4-1.6 bottom bailout.

[wedivebc]

Even though OxTox has been observed at 0.5ATA, so its not watertight.


Do you have a reference for that Chris. I had not heard about a tox event below 1.2 before

[Cave Diver]

Do you have a reference for that Chris. I had not heard about a tox event below 1.2 before

I have heard of at least one incident of tox occurring in the 1.0-1.2 range and I *think* there was a discussion Thal was involved in that mentioned once incident significantly lower. I'll ask him to chime in if he recalls.

[cruiser]

OC - 1.2

I don't have tech training and do recreational diving only so far.

[Jax]

So it sounds like everyone keeps to the NOAA recommendations as a minimum, but lowers the PPO2 for working, current, and/or time. Deco seems to be kept the same?

[Dr Wu]

Strange distinction. Don't you trust your buoyancy control?

You never know when you are going to drop your donut.

[Tortuga68]

That's a bit higher than the norm. Is this based on agency/training recommendations or personal risk assessment?

The latter. No agency would be dumb enough to put their name to it, if only for liability reasons. It's pushing it, but I know enough people who have done it that I'm not too uncomfortable, given my personal considerations. I'll give 2.31 a go some time, but probably just for one dive

[Cave Diver]

The latter. No agency would be dumb enough to put their name to it, if only for liability reasons. It's pushing it, but I know enough people who have done it that I'm not too uncomfortable, given my personal considerations. I'll give 2.31 a go some time, but probably just for one dive

What kind of exposure time to you plan for with a 2.0 PO2?

[Tortuga68]

Very short ones

[Jax]

The latter. No agency would be dumb enough to put their name to it, if only for liability reasons. It's pushing it, but I know enough people who have done it that I'm not too uncomfortable, given my personal considerations. I'll give 2.31 a go some time, but probably just for one dive

So, if my calculations are correct, that would be EAN40 to 165'fsw? (On the fly, so might be wrong. :) ) Is a PPO2 of 2.0 something you do often?

[LiteHedded]

The latter. No agency would be dumb enough to put their name to it, if only for liability reasons. It's pushing it, but I know enough people who have done it that I'm not too uncomfortable, given my personal considerations. I'll give 2.31 a go some time, but probably just for one dive

sounds like a dive you might be able to only pull off once

[Wookie]

2.0 scootering trimix, 1.6 swimming trimix, 2.0 deco. I've never heard the Wah Wah's. But my lovely bride, OTOH, hears them anytime over 1.2, so I mix gas for the both of us for a 1.2, and we deco together.

[PfcAJ]

I just don't see the point of pushing something like ppo2.

[Jax]

2.0 scootering trimix, 1.6 swimming trimix, 2.0 deco. I've never heard the Wah Wah's. But my lovely bride, OTOH, hears them anytime over 1.2, so I mix gas for the both of us for a 1.2, and we deco together.

Thanks, Wookie -- will you help a newb understand why, or the reasoning behind, going that high?

I've read enough history to know the early divers went that high . . .

[Tortuga68]

I just don't see the point of taking PP02 as the single, defining measure of a dive without taking exposure into consideration

[PfcAJ]

Anyone can get delayed.

[Jax]

I just don't see the point of taking PP02 as the single, defining measure of a dive without taking exposure into consideration

I can understand that, I have met people that routinely deco at PPO2 = 2.0. They have good reasons, IMO, and it works for them. It wouldn't work for me at my current level of risk adversity.

So what kind of dive would you take the PPO2 to that level? I'm just trying to understand something I hadn't considered before.

[LiteHedded]

Anyone can get delayed.

not superdivers.
internet heroes can pull it off. its a measure of the ratio of chest hair to brains

[Jax]

I just don't see the point of pushing something like ppo2.


Anyone can get delayed.


not superdivers.
internet heroes can pull it off. its a measure of the ratio of chest hair to brains

*ahem* . . . can we learn about why people do what they do without getting snarky? Please?

[LiteHedded]

in fairness, AJ wasn't being snarky.

I was though. I dont like the idea of promoting stuff like this on the internet. people die from this.

[PfcAJ]

Man, this one one of those time I actually wasn't being snarky.

[Jax]

in fairness, AJ wasn't being snarky.

I was though. I dont like the idea of promoting stuff like this on the internet. people die from this.

I disagree that information in and of itself causes people to die. It is the person's inability to apply critical thinking and assess the risk in relation to themselves in applying that information that causes people to die. Most call this Darwinism.

I do not have to agree with people's standard of safety or reason to learn about their thought processes. I just want to hear their side of the story.

[Tortuga68]

sounds like a dive you might be able to only pull off once


not superdivers.
internet heroes can pull it off. its a measure of the ratio of chest hair to brains

Welcome to Scubaboard folks, where if you express a different opinion to some people you're an internet hero and YOU'RE GUNNA DIE!!1!

[PfcAJ]

Obviously words alone do not cause deaths, Jax.

However, bad information can and does cause deaths. If no one says "hey, thats unsafe" and others read it and emulate it, they could get injured or killed.

[Wookie]

Thanks, Wookie -- will you help a newb understand why, or the reasoning behind, going that high?

I've read enough history to know the early divers went that high . . .

I get bored hanging on a rope at 30, 20, 10 feet. I learned from early divers. I've done a table 6. The table 6 has far far higher exposures than 2.0, and I wasn't affected by the exposure (well, except for this re-curring twitch :D ). I don't ever want to do another table 6 again. I'm not likely to spend more than 20 min on the bottom at those exposures anyway. I'm scared of rebreathers.

[PfcAJ]

Wookie, you do know that an immersed person is more susceptible to a toxic episode than a dry one, correct? I'm also sure that you know there is wild variation between subjects and within subjects in regards to exposure needed to cause a toxic episode, right?

[ScubaFeenD]

I get bored hanging on a rope at 30, 20, 10 feet. I learned from early divers. I've done a table 6. The table 6 has far far higher exposures than 2.0, and I wasn't affected by the exposure (well, except for this re-curring twitch :D ). I don't ever want to do another table 6 again. I'm not likely to spend more than 20 min on the bottom at those exposures anyway. I'm scared of rebreathers.

No offense, but when you get hyperbaric O2 in a medical setting, seizing isnt a big deal. When you seize at depth, you have a reasonably high likelihood of dying.

[LiteHedded]

I get bored hanging on a rope at 30, 20, 10 feet. I learned from early divers. I've done a table 6. The table 6 has far far higher exposures than 2.0, and I wasn't affected by the exposure (well, except for this re-curring twitch :D ). I don't ever want to do another table 6 again. I'm not likely to spend more than 20 min on the bottom at those exposures anyway. I'm scared of rebreathers.

you also weren't underwater. and your sample size is pretty low.



I disagree that information in and of itself causes people to die. It is the person's inability to apply critical thinking and assess the risk in relation to themselves in applying that information that causes people to die. Most call this Darwinism.

I do not have to agree with people's standard of safety or reason to learn about their thought processes. I just want to hear their side of the story.

well we circumvent natural selection every day don't we? a purely darwinian world is not a world I would want to live in.

[Wookie]

Obviously words alone do not cause deaths, Jax.

However, bad information can and does cause deaths. If no one says "hey, thats unsafe" and others read it and emulate it, they could get injured or killed.

I understand your way of thinking, and applaud it. I've come to understand, however, that everyone's physiology is different, and different exposures effect folks differently. For instance. One of my buddy's suffers from Nitrogen slam. I don't. My wife suffers during high exposures of oxygen. I don't. I am useless from narcosis at 100 feet. I'm so happy Billy Deans invented helium, I can't hardly stand it.

This is not a 'You should go out and do this" kind of thread, nor is it a "hold my beer and watch this" kind, either. This is a "what are your tolerances for risk" type of thread. I would hope every diver limits their exposure to whatever (cold, O2, He, N2, abusive DM's) to something within their comfort zone/experience level, and when they want to push the envelope, they get the proper training/mentoring to do so safely. I don't dive solo with a PO2 of 2.0, but I do make those dives. My buddy is well aware of my gas planning.

[Jax]

Um, guys, we're talking about Wookie, here.

I'm not sure, but he may have more hours underwater than y'all have on this Earth . . . . ;)

[ScubaFeenD]

I'm not sure, but he may have more hours underwater than y'all have on this Earth . . . . ;)

There are some things that you just cant get around with number of dives. Increasing age and definite human physiological susceptibility to ox tox are two of em. Just because it hasn't gotten you yet doesn't mean it wont, and in a world with gases that can decrease, significantly, the risk, why would you bother taking the risk? IJS

Also, i dont know wookie.

[Wookie]

Wookie, you do know that an immersed person is more susceptible to a toxic episode than a dry one, correct? I'm also sure that you know there is wild variation between subjects and within subjects in regards to exposure needed to cause a toxic episode, right?

There is also a wild variation between the same subject day to day and season to season as conditions change. And, yes, I understand that seizing in a chamber with a tech present to get your tongue out of your throat is different than spitting a regulator underwater.

Guys, I'm not advocating anyone else jump on out and determine your max tolerance to O2 for a given situation. At the point where anyone is worrying about O2 toxicity issues, they should have, however, a pretty fair knowledge of THEIR comfort level and response to physiological stimuli. I have gained the knowledge over a couple hundred dives that I'm not as susceptible UNDER PERFECT CONDITIONS to suffering from an O2 event as training standards are written for. I am, however more susceptible to DCS and narcosis than tables allow for. Frankly, I'm tired of being bent. All 3 were not deserved by table and dive computer. Obviously I deserved them, I got them. I don't have a PFO, I just seem to retain N2 more than most.

[wedivebc]

So it sounds like everyone keeps to the NOAA recommendations as a minimum, but lowers the PPO2 for working, current, and/or time. Deco seems to be kept the same?

That is how divers tend to apply the limits now. It wasn't long ago the USN was recommending 2.0 as a practical limit to oxygen toxicity but have dialed it back in the last 10 years or so. If you notice from the above posts there have been (rare) cases of tox events below these limits and we may see some further dialing back as time goes on. Many tech divers are discovering the small decompression penalty they pay for lower PO2 may well offset the higher risk of higher PO2. But only time will tell just how great that risk is.

[Jax]

<sigh> Can we just reach for understanding here, instead of arguing someone's personal decision?

Look, we know NOAA recommends 1.4 or less, and 1.6 PPO2 as an absolute max. Fine. It's the current accepted norm.

However, some people make a decision to do something else. That is okay. It is not our place to attack them or try to change their mind.

I would like to know why people do the things they do; in this case, they dive to a higher that accepted 'norm' of PPO2. I am going to ACCEPT that the people that do this are not stupid, that they made the decision for themselves, and it's not my place to tell them they are wrong.

[Jax]

That is how divers tend to apply the limits now. It wasn't long ago the USN was recommending 2.0 as a practical limit to oxygen toxicity but have dialed it back in the last 10 years or so. If you notice from the above posts there have been (rare) cases of tox events below these limits and we may see some further dialing back as time goes on. Many tech divers are discovering the small decompression penalty they pay for lower PO2 may well offset the higher risk of higher PO2. But only time will tell just how great that risk is.

Super! Thank you! :clapping:

[LiteHedded]

Um, guys, we're talking about Wookie, here.

I'm not sure, but he may have more hours underwater than y'all have on this Earth . . . . ;)

that means exactly nothing to me. not that I'm slamming him in particular.

[Jax]

There are some things that you just cant get around with number of dives. Increasing age and definite human physiological susceptibility to ox tox are two of em. Just because it hasn't gotten you yet doesn't mean it wont, and in a world with gases that can decrease, significantly, the risk, why would you bother taking the risk? IJS

My point exactly!!! I want to know why people choose to take that risk.


Also, i dont know wookie.

I trust that Wookie knows Wookie. ;)

[Rainer]

1.4 max bottom, 1.2 planned bottom for deeper dives, 1.6 for deco.

[Jax]

Welcome to Scubaboard folks, where if you express a different opinion to some people you're an internet hero and YOU'RE GUNNA DIE!!1!

Now you cut it out, too! You haven't told us about why you punch up the PPO2! :scorned:

[LiteHedded]

My point exactly!!! I want to know why people choose to take that risk.



I trust that Wookie knows Wookie. ;)

nickel rocketry and deco weinery?

ok I've had my fun. I'll leave this thread to you guys and crawl back to my tech section

[Jax]

nickel rocketry and deco weinery?

ok I've had my fun. I'll leave this thread to you guys and crawl back to my tech section

Aren't you curious why people would do something? I like to know how a race motorcycle rider countersteers through the turns . . . . I don't want to run out and try it. :)

[Kevin Carlisle]

Aren't you curious why people would do something? I like to know how a race motorcycle rider countersteers through the turns . . . . I don't want to run out and try it. :)

On flat track they use weight and throttle, on motocross they use weight, muscle, throttle and brakes. On sport bikes its weight, throttle and their knee :D

[LiteHedded]

Aren't you curious why people would do something? I like to know how a race motorcycle rider countersteers through the turns . . . . I don't want to run out and try it. :)

I think they do it because they have inappropriate exposure protection to do the deco they signed up for. so they push ppo2 on the bottom to reduce it, instead of spending money on equipment. Or they'll dive air deep to save money on helium. relying on nitrogen being a CNS depressant to stave off a toxic event on the bottom.

or some of them just want to see what will happen. it doesn't much matter to me.

the problem being, Johnny Scubaboard comes along and sees the people doing this have tons of technical training listed in their profile or they're an instructor, and people on here say oh that's so-and-so he has tons of dives so he must know what he's doing. then johnny goes out to some deep wreck or eagle's nest and bites it.

there is a reason the max acceptable ppo2 has been scaled back. it's not just for $h!ts and giggles ;)

[Jax]

On flat track they use weight and throttle, on motocross they use weight, muscle, throttle and brakes. On sport bikes its weight, throttle and their knee :D

:rofl3: And how many bones have you broken? :blinking:


:focus:

As mentioned before, the Navy used to find a max PPO2 of 2.0 acceptable. In the past 10-15 years, they've dialed it back to a max of 1.6.

So -- I'm asking for a SWAG here -- What kind of percentage of injury /death is acceptable?

If a max PPO2 resulted in 1% deaths and 3% incidences of OxTox . . . (that's a made-up statistic!) say, over a year.

And now the max PPO2 = 1.6 is resulting in .1% deaths and 1% incidences over a year . . .

What's acceptable?

[Jax]

the problem being, Johnny Scubaboard comes along and sees the people doing this have tons of technical training listed in their profile or they're an instructor, and people on here say oh that's so-and-so he has tons of dives so he must know what he's doing. then johnny goes out to some deep wreck or eagle's nest and bites it.

there is a reason the max acceptable ppo2 has been scaled back. it's not just for $h!ts and giggles ;)

I agree with the last part; with some digging, I could find it.

But for the first part . . . . when are we going to stop being responsible for every stupid Tom, Dick, and Harry? Shall we all do like the auto industry's "Closed course, professional driver, do not attempt", and put "Personal decision for this diver, do not attempt" in our sig blocks? :shakehead:

You can try to make things fool proof, but a better fool will come along.

[Kevin Carlisle]

:rofl3: And how many bones have you broken? :blinking:


:focus:

As mentioned before, the Navy used to find a max PPO2 of 2.0 acceptable. In the past 10-15 years, they've dialed it back to a max of 1.6.

So -- I'm asking for a SWAG here -- What kind of percentage of injury /death is acceptable?

If a max PPO2 resulted in 1% deaths and 3% incidences of OxTox . . . (that's a made-up statistic!) say, over a year.

And now the max PPO2 = 1.6 is resulting in .1% deaths and 1% incidences over a year . . .

What's acceptable?

Enough. Only one on a motorcycle tho.

[LiteHedded]

I agree with the last part; with some digging, I could find it.

But for the first part . . . . when are we going to stop being responsible for every stupid Tom, Dick, and Harry? Shall we all do like the auto industry's "Closed course, professional driver, do not attempt", and put "Personal decision for this diver, do not attempt" in our sig blocks? :shakehead:

You can try to make things fool proof, but a better fool will come along.

I'm not going to police anyone. but I will call a spade and idiot where I see it ;)

[Jax]

I'm not going to police anyone. but I will call a spade and idiot where I see it ;)

:depressed:

[LiteHedded]

oh come on! with the nice libertarian ideals in that last post of yours surely you're not going to be the PC police on me? :D lol

[Wookie]

Litehedded and I are not likely to dive together anyway. I rig hogarthian, and he is DIR. I, however, do not express my opinion about folks who are DIR. I applaud him for knowing his limits and staying in his comfort zone. :D

[LiteHedded]

Litehedded and I are not likely to dive together anyway. I rig hogarthian, and he is DIR. I, however, do not express my opinion about folks who are DIR. I applaud him for knowing his limits and staying in his comfort zone. :D

aw I'd dive with you! with a reasonable ppo2 that is :)

it has nothing to do with DIR and I'm not talking about you in particular. it's not personal and I generally enjoy your posts (and tortuga's for that matter)

but why do you push your ppo2 though? now I'm curious like Jax.

this whole thing reminds me of an article I read in the NACD journal or the NSSCDS magazine. it was a widow writing about the dives her husband used to do before he toxed

[Jax]

oh come on! with the nice libertarian ideals in that last post of yours surely you're not going to be the PC police on me? :D lol

Is it working? :blinking:

[Wookie]

aw I'd dive with you! with a reasonable ppo2 that is :)

it has nothing to do with DIR and I'm not talking about you in particular. it's not personal and I generally enjoy your posts (and tortuga's for that matter)

but why do you push your ppo2 though? now I'm curious like Jax.

this whole thing reminds me of an article I read in the NACD journal or the NSSCDS magazine. it was a widow writing about the dives her husband used to do before he toxed

I don't consider it pushing it. It's how I was trained and it has worked for me in the past. I'm not stuck with those numbers either. As I said on my first post, my wife and normal dive buddy doesn't tolerate O2 well, so when we dive together, I mix for a 1.2 max, both deco and bottom. When I dive with my emergency backup buddy (who just switched to rebreather, so I likely won't dive with her anymore) she must have about 20% He in her deep deco mix, so I deco on 32/20. It's all about the situation. I hate mixing gas, so if I mix it, I tend to make a bunch and adjust my diving appropriately.

I'm just not fearful of it.

Edit: That was not a good way to say the last sentence. I just don't give it as wide a berth as others might.

[Jax]

I don't consider it pushing it. It's how I was trained and it has worked for me in the past. I'm not stuck with those numbers either. As I said on my first post, my wife and normal dive buddy doesn't tolerate O2 well, so when we dive together, I mix for a 1.2 max, both deco and bottom. When I dive with my emergency backup buddy (who just switched to rebreather, so I likely won't dive with her anymore) she must have about 20% He in her deep deco mix, so I deco on 32/20. It's all about the situation. I hate mixing gas, so if I mix it, I tend to make a bunch and adjust my diving appropriately.

I'm just not fearful of it.

Edit: That was not a good way to say the last sentence. I just don't give it as wide a berth as others might.

So - You trained early in diving to a PPO2 of 2.0, know you aren't as susceptible to OxTox as some, and due to your personal history, find the risk of DCS greater than the risk of OxTox . . . did I get that right?

[Cave Diver]

This is not a 'You should go out and do this" kind of thread, nor is it a "hold my beer and watch this" kind, either. This is a "what are your tolerances for risk" type of thread. I would hope every diver limits their exposure to whatever (cold, O2, He, N2, abusive DM's) to something within their comfort zone/experience level, and when they want to push the envelope, they get the proper training/mentoring to do so safely. I don't dive solo with a PO2 of 2.0, but I do make those dives. My buddy is well aware of my gas planning.

I don't agree with your choice of PO2's but I do agree with your reasoning. I've only met you in person once, but we know enough of the same people that I know you've got enough experience and training to make this decision and risk assessment for yourself. It's not something I'd make a habit of, but I certainly won't be the one telling you not to either. Now if you were inexperienced or untrained, that might be a different story...

Years ago I've did a high PO2 dive with a buddy who experienced Wah Wah's and early signs of ox tox while I was completely unaffected. It provided for an interesting couple of minutes. Different people have different tolerances.

There are a lot of people who tweak deco schedules based on how they feel during or after a dive. It's a matter of listening to your body and you're the person who knows it best.

[Wookie]

So - You trained early in diving to a PPO2 of 2.0, know you aren't as susceptible to OxTox as some, and due to your personal history, find the risk of DCS greater than the risk of OxTox . . . did I get that right?

Yes. Now, if you were my student, we would train at 1.4/1.2. While we were diving together, we might plan a dive for 1.6/1.4, after you were certified. If conditions dictated (we already had mix in our cylinders, the wreck had settled, we needed to recover the anchor that was hung in the wreck), we MIGHT plan a dive for 1.6/2.0 as long as we BOTH felt comfy, we understood the need to make the dive, and we understood the risks. If you had never been to that high PO2, we wouldn't do it on a dive where we had a mission to accomplish, because, even though we both know our limitations, when you have a mission, it tends to cloud your judgment to other things going on around you (perception narrowing) and you might not notice the effects the high PO2 was having on your body. If you felt the least bit uncomfortable making such a dive with me, we would re-mix our gas to the place where you felt comfortable. After all, there is NOTHING in the ocean worth dying for, including your buddy. Adding a bit of helium to any mix lowers your PO2. It's not that big a deal. I don't usually find that high pO2 is a trimix issue in any case, it's usually a deep air/nitrox issue.

OBTW, the tech diving rules on the Spree for all divers including crew are max PO2 of 1.6, and a deep air limit of 150 feet.

That frickin' penguin is quite distracting, I'll have you know. Not that I want it to go away. IJS

[ScubaFeenD]

There are a lot of people who tweak deco schedules based on how they feel during or after a dive. It's a matter of listening to your body and you're the person who knows it best.

You know, Ive met people that say that about drunk driving too. I guess we should be OK with people that feel fine to drive no matter what, huh?

Point for me is this: People can say whatever they want. Maybe they are more or less susceptible to ox tox (there is personal variation for sure), but every time you risk the need for a rescue response you put OTHERS at risk. The issue with too limited a view is that you only see the one person as at risk, when that really isnt the case. The industry has defined 1.6 as the acceptable risk level, and beyond that you are being stupid. Not that you ARE stupid, just that you are making a stupid decision. Maybe if there were no gases available to prevent it, it would be a different issue, BUT THERE ARE. So, my point, is why would you bother risking a ppO2 of 2.0 when you dont have to.


OF course, if you wear a full-facemask things are a bit different, but no one here seems to have justified their ppO2 based on that...so I will assume that it isnt being used.

[Cave Diver]

So, my point, is why would you bother risking a ppO2 of 2.0 when you dont have to.

Did you bother to read his post? Or my response for that matter? Or are you just too caught up in one or two lines to see the bigger picture?

[ScubaFeenD]

deleted post

[Cave Diver]

Yes I read it, and you didn't answer my question sufficiently. Perhaps you should try re-reading your post; You didn't address any reason why you would go beyond a generally acceptable safety limit--how you feel generally means squat as a reason. Do you often disregard what is considered safe based on how you feel?

BTW, my comment quoted you, but it wasn't necessarily directed at you. It was more a general rhetorical question.

If you read my post you'll note that I don't agree with his choice of PO2's - as in I wouldn't personally dive those limits. However he's demonstrated a known susceptibility to DCS and a tolerance to oxtox. Given his circumstances, his choice is right for him. I respect his right to make that choice knowing that he likely has more training and experience than you and I combined.

I also emphasized listening to what your body is telling you. Many people can feel the symptoms of subclinical DCS by the way the feel during and after a dive. There are divers that tweak their schedules in the water based on how they feel to either get out faster, or hang longer.

There are also indicators to high O2 exposure prior to convulsing. That is the result that happens when you ignore the other signs. Have you experienced any of these effects for yourself? Some of us have and we speak from experience, not just something we read in a book.

I'm not advocating widespread use of high PO2's. I'm advocating that responsible divers making informed decisions have the right to do so if they choose. They know the risks, they understand them and they accept them. Perhaps you missed this part of my post as well?


Now if you were inexperienced or untrained, that might be a different story...

[Wookie]

Point for me is this: People can say whatever they want. Maybe they are more or less susceptible to ox tox (there is personal variation for sure), but every time you risk the need for a rescue response you put OTHERS at risk. The issue with too limited a view is that you only see the one person as at risk, when that really isnt the case. The industry has defined 1.6 as the acceptable risk level, and beyond that you are being stupid. Not that you ARE stupid, just that you are making a stupid decision. Maybe if there were no gases available to prevent it, it would be a different issue, BUT THERE ARE. So, my point, is why would you bother risking a ppO2 of 2.0 when you dont have to.

Which brings up a whole new issue, but is related. I learned to dive when PO2's were acceptable at 2.0. Trimix was something Billy Deans was teaching down in Key West, but divers were successfully diving the Doria and other wrecks on air. My friend Ian was diving a AP rebreather on Trimix before TDI was even a dream of Bret Gillam's. Nitrox was the evil gas that PADI said they'd never endorse, and DEMA followed suit.

Now, you tell me that 1.6 is an "Industry Standard" because someone published it in a book somewhere, my friend Ian had to get a certification card to do something he's been doing since before there were certification cards for it, and I'm making a stupid decision because I'm following the standards of the time I was trained. PADI issues C-Cards to divers diving voodoo gas without requiring them to make a dive using the gas.

I'm all for learning from mistakes. One of the problems with the industry is that folks make up "industry standards" with no basis for them. We've determined in this thread that some divers are more susceptible to ox-tox than others, some can tox at PO2's of 1.2 or less, and that some of us aren't as prone to suffering from ill effects of O2 than others. What are these industry standards supposed to do? Keep us safe? DIVING ISN'T SAFE, AND ANYONE WHO TELLS YOU IT IS IS BLOWING SMOKE UP YOUR ASS. Diving is a sport that carries some risk. It is up to each of us to define what level of risk we are willing to accept to accomplish our goals. When someone dies in the #3 pumproom of the Spiegel Grove, I don't say to myself "What an idiot!", I say "well, he tooks his chances and paid the price". I don't penetrate caves or wrecks because it's OUT OF MY COMFORT ZONE. I don't think that people who do are stupid, I just don't do it myself.

And your comment about placing others at risk is hogwash. Anyone on a search and recovery team is there because they understand the risks, and have weighed them and decided to join the team anyway. They do so for their own reasons, not to meet some "Industry Standard". Once again, that kind of risk is beyond my comfort zone, because I believe that a dead body is not worth risking my life for. Props to those who do, they perform an important service to the family, and I applaud them for their dedication.

I've seen recreational divers bent on air at depths and times that were completely a mystery to me as to why they suffered a hit. Gases are available to prevent this. Should we all squirt some helium in our air to eliminate DCS? No, because helium doesn't eliminate DCS any more than diving at a 1.2 PO2 eliminates Oxygen Toxicity. So the industry defines drowning as one of the risks of diving. If you go diving, you are making a stupid decision because you may drown. Think about that the next time you make the decision to dive.

[ScubaFeenD]

There are also indicators to high O2 exposure prior to convulsing. That is the result that happens when you ignore the other signs. Have you experienced any of these effects for yourself? Some of us have and we speak from experience, not just something we read in a book.

I'm not advocating widespread use of high PO2's. I'm advocating that responsible divers making informed decisions have the right to do so if they choose. They know the risks, they understand them and they accept them. Perhaps you missed this part of my post as well?

Always? I am not aware that there are always warning signs, or that if there are you have enough time to react. Even if you DO notice the effects some of the time there is no guarantee that it will happen every time. Do you have information that I am not aware of? Regardless, i dont really care if you make a decision that ends up with you drowning--hopefully it wont effect my life with some silly regulation or further restrictions on diving. What I care about I might address below.




Now, you tell me that 1.6 is an "Industry Standard" because someone published it in a book somewhere, my friend Ian had to get a certification card to do something he's been doing since before there were certification cards for it, and I'm making a stupid decision because I'm following the standards of the time I was trained. PADI issues C-Cards to divers diving voodoo gas without requiring them to make a dive using the gas.

I'm all for learning from mistakes. One of the problems with the industry is that folks make up "industry standards" with no basis for them.

...edited...

And your comment about placing others at risk is hogwash. Anyone on a search and recovery team is there because they understand the risks, and have weighed them and decided to join the team anyway. They do so for their own reasons, not to meet some "Industry Standard". Once again, that kind of risk is beyond my comfort zone, because I believe that a dead body is not worth risking my life for. Props to those who do, they perform an important service to the family, and I applaud them for their dedication.

Just because "standards" get changed doesnt mean they are wrong, they are just modified as more information comes in; its a natural side effect of an evolving understanding.


Further, my assertion is not hogwash. I was in the fire service for many years, and I have seen many accidents happen (fires, auto accidents, etc) and some of them were caused by reckless disregard for safety, which then put people in charge of rescuing those people under undo risk as well. Sometimes rushing to a scene and putting your life on the line for someone who legitimately had an unfortunate event happen is one thing, putting your life on the line for someone who was knowingly disregarding a generally accepted safety limit is completely another. So maybe it isnt a recover team, maybe it is a coast guard vessel that rushes to pick your a$$ up after you decide to disregard a limit that research has determined to be acceptable just because you feel like its ok. That isnt ok in my book, and sadly rescuers cant opt out of a rescue because someone was just doing something stupid.

You will probably just disregard this too as too far out there, but its a common concern in the first response community, and until you know someone who dies because of stupidity you will probably never understand.



I've seen recreational divers bent on air at depths and times that were completely a mystery to me as to why they suffered a hit. Gases are available to prevent this. Should we all squirt some helium in our air to eliminate DCS? No, because helium doesn't eliminate DCS any more than diving at a 1.2 PO2 eliminates Oxygen Toxicity. So the industry defines drowning as one of the risks of diving. If you go diving, you are making a stupid decision because you may drown. Think about that the next time you make the decision to dive.

I wasnt aware the reason for helium use is for the purpose of DCS risk decrease. From what I understand it can, in fact, actually increase the risk of more serious DCS.

Anyway, I am really bored with this and since neither side will budge (im sure) lets just call truce and discuss more serious topics such as whether split fins will kill you , huh?

[down4fun]

my responses are pretty much in line with everyone else. When I was diving straight nitrox I would almost always dive 1.6 especially for the deeper recreational dives. Why? higher O2 give me a longer bottom time, the CNS exposure was not going to be anywhere near 100% as the bottom times were short. I never had a twinge.
For light tech I would go 1.4 bottom gas down to 200ft and 1.6 for deco. Why it is a generally accepted standard and at that point I had helium in the mix so 1.4 was acceptable yet still gave me adequate bottom time.
For CCR I run 1.2 for the dive and 1.6 for deco. Why? Again it's pretty standard and I see no need for what I am diving to push the limits. My bailout I will push to 1.6 but really just because it's what i have (for instance 18/45 on a 256ft dive) and the PO2 is for the absolute bottom and once i bailout i will be ascending almost immediately. Plus I already have a tank farm of bailouts so I am not going to dump 80cuft of 18/45 to get 10/50 for one dive to that depth. On long shallow runs, ie 3 hours at 70ft i may back down to 1 to reduce the O2 exposure.
Just my .02

[Wookie]

Anyway, I am really bored with this and since neither side will budge (im sure) lets just call truce and discuss more serious topics such as whether split fins will kill you , huh?

I'm up with that. So, if you put pure O2 in your SpareAir, will you die on deco?

[Cave Diver]

I'm up with that. So, if you put pure O2 in your SpareAir, will you die on deco?

Only if you deco deeper than 30'. The question is, will you die from OxTox, or from running out of deco gas after 3 minutes?

[Jax]

I'm up with that. So, if you put pure O2 in your SpareAir, will you die on deco?

It depends . . . is your mask on your forehead?

[ScubaFeenD]

I'm up with that. So, if you put pure O2 in your SpareAir, will you die on deco?

Only if you don't shake it before use.

[PfcAJ]

I wasnt aware the reason for helium use is for the purpose of DCS risk decrease. From what I understand it can, in fact, actually increase the risk of more serious DCS.



Well, some (myself included) think that helium helps reduce DCS is used properly. However, botching the deco can have some serious effects, as well.

[rjack321]

Why jack the ppO2 on the bottom phase at all? So you have ~5-10mins more deco, big whoop just do some extra time.

[LiteHedded]

deco weenery
there haven't been any responses that don't amount to shaving a tiny amount of deco or saving money

[halemanō]

Alright, I'm an NDL diver who would push a gentle 1.8 max depth for the right reason(s). My non-deco IANTD Nitrox training was 1.6/1.8. Still a 3 minute SS and tank price unchanged.

[Tortuga68]

there haven't been any responses that don't amount to shaving a tiny amount of deco or saving money

Maybe if you took your fingers out of your ears and stopped chanting "lalala deco weenery lalala nickel rocketry lalala internet heroes lalala idiots lalala superdivers lalala" you might hear some

[LiteHedded]

Maybe if you took your fingers out of your ears and stopped chanting "lalala deco weenery lalala nickel rocketry lalala internet heroes lalala idiots lalala superdivers lalala" you might hear some

Im all ears
go on...

[DiveNav]

based on my experience (I actually died few times of OxTox) I am now more concerned about the actual CNS % value (that I try to keep < 80%) than the PO2 absolute value per se.

Having said that, on OC I might allow a PO2 of 1.6, but when on CCR I program the Predator Set Point H to <1.2 (and I descend slowly)

Alberto (aka eDiver)

[ScubaFeenD]

based on my experience (I actually died few times of OxTox)

I am very sorry to hear that :-/

[DiveNav]

I am very sorry to hear that :-/
Don't worry .... it happened only in the sim :D

[Jax]

based on my experience (I actually died few times of OxTox) I am now more concerned about the actual CNS % value (that I try to keep < 80%) than the PO2 absolute value per se.

Having said that, on OC I might allow a PO2 of 1.6, but when on CCR I program the Predator Set Point H to <1.2 (and I descend slowly)

Alberto (aka eDiver)


Don't worry .... it happened only in the sim :D

:rofl3: :rofl3: :rofl3:

It seems to me that those of us who certified later had the fear of [-]God[/-] OxTox drilled into us so heavily that it's hard to look at that 2.0 or 1.8 thingy with objectiveness.

[String]

1.4 bottom for me unless i know im expecting to work then maybe 1.2 or 1.3. That's rare though.

1.6 always for deco.

[peterbj7]

those of us who certified later had the fear of [-]God[/-] OxTox drilled into us so heavily that it's hard to look at that 2.0 or 1.8 thingy with objectiveness

I certified pretty early on, and well remember one liveaboard at Tiran when I did 7 dives a day for three days, the first four each day being to below 75msw. All on air with some standard nitrox to speed up deco. I'm not sure I'd do that nowadays, but then I suffered no ill effects.

[kanonfodr]

:rofl3: :rofl3: :rofl3:

It seems to me that those of us who certified later had the fear of [-]God[/-] OxTox drilled into us so heavily that it's hard to look at that 2.0 or 1.8 thingy with objectiveness.

The way I like to think about it is as a direct proportion: higher po2 equals a higher risk for the chance of something happening. Some friends of mine had to chase down some dumb*** divers on a charter about a month ago. They hit 136 fsw on EANx36. Both had no issues. How lucky do you feel?


BTW, 1.4 bottom with an allowable of 1.5 for seeing something REALLY cool but we aren't hanging around for long in that case. I don't do deco yet.

Peace,
Greg

[Searcaigh]

1.4 for me throughout the whole dive

[ScubaFeenD]

The way I like to think about it is as a direct proportion: higher po2 equals a higher risk for the chance of something happening.

Yeah, that is the idea behind the oxygen clock, but you can still have only a few minutes of exposure and develop symptoms of CNS ox tox.

[John_B]

Same as it ever was: 1.4

[peterbj7]

Yeah, that is the idea behind the oxygen clock

Only a technicality, but I disagree. The oxygen clock assumes a maximum possible exposure measured by time, which you then progress towards as time passes. the chance element is a different theory.

[ScubaFeenD]

Only a technicality, but I disagree. The oxygen clock assumes a maximum possible exposure measured by time, which you then progress towards as time passes. the chance element is a different theory.

I was referring more to the dose response aspect; as dose of high pO2 increases you reach a point determined to be 100%, where the likelihood of experiencing tox has been determined to be very high. Obviously, it's not all or none, as would be expected by a dose response curve. Some people can go beyond the 100% mark and not get toxed, and some people cant get to the 10% mark at some pO2s.

The clock component is the idea that you only have a certain number of minutes at a specific pO2. So on technicality you may be right. Thanks for pointing that out :)

[Wookie]

BTW, 1.4 bottom with an allowable of 1.5 for seeing something REALLY cool but we aren't hanging around for long in that case. I don't do deco yet.


I might suggest that a limit of 1.4 "unless we see something REALLY cool" is not a dive plan, but is a good way to get hurt. So, what if there is something REALLY REALLY cool 10 feet deeper. and what if something is ULTRA cool 10 feet below that. Where does the coolness end and the dive planning begin?

Dive plans are not made to change on the fly. Dive plans are hard, fast, and absolute, unless an unexpected event causes you to call the dive earlier or at a shallower depth. I was taught to cut a set of tables 10 feet deeper and 5 minutes longer than my actual dive plan. I think that's silly. I cut a set 10 feet shallower and 5 min shorter just in case I leave the bottom earlier than I planned, but I'm not going deeper or staying longer than I planned, because you can always come back later to see whatever is REALLY cool deeper.

[kanonfodr]

Wookie,

I'm not trying to slam you and your dive practices, but I consider the dive plan something that is resolved but malleable underwater if the team agrees to it. If we drop in and the current is heavier than predicted, or going the wrong way, or whatever then we adjust our plan to conform to conditions in the water.

But the key is having a skilled, disciplined team that can work and think together both above and below the water's surface. And if the team leader is doing something that one of the other members isn't comfortable with, we pull back and do something not so scary. Otherwise, he's the leader and while he is in charge, IMO the leader is also charged with making sure everyone has a good, enjoyable dive.

And if we see something really cool that's 10 feet deeper, then we can take a quick peek down there since we are planning our dive pretty conservatively on the surface, and keeping our brains engaged during the dive. So we may plan a PO2 of 1.2, and if we see something really cool 10 feet lower it's not a problem. And we have 2 or 3 more levels of Really Cool before it's an issue.

Peace,
Greg




I might suggest that a limit of 1.4 "unless we see something REALLY cool" is not a dive plan, but is a good way to get hurt. So, what if there is something REALLY REALLY cool 10 feet deeper. and what if something is ULTRA cool 10 feet below that. Where does the coolness end and the dive planning begin?

Dive plans are not made to change on the fly. Dive plans are hard, fast, and absolute, unless an unexpected event causes you to call the dive earlier or at a shallower depth. I was taught to cut a set of tables 10 feet deeper and 5 minutes longer than my actual dive plan. I think that's silly. I cut a set 10 feet shallower and 5 min shorter just in case I leave the bottom earlier than I planned, but I'm not going deeper or staying longer than I planned, because you can always come back later to see whatever is REALLY cool deeper.

[peterbj7]

Dive plans are hard, fast, and absolute, unless an unexpected event causes you to call the dive earlier or at a shallower depth

I don't agree with that. For any serious dive I always have a range of plans, and can switch between them for whatever reason. There will indeed be limits beyond which I won't go, probably, depending just what the implications of such a divergence might be.

For helium dives I'm much more strict with myself, because the effects of helium aren't well understood and I have no desire to get a helium bend under water.

[LiteHedded]

changing dive plans in the water is no big deal. stuff happens

[Wookie]

Well. I guess we've all found where we think someone elses decisions are decisions we wouldn't make ourselves. Ain't freedom grand?

And I don't feel slammed, I do things some don't agree with also. But to me, if you're going to change your plan on the fly, you'd better have discussed it on the surface, and, if you've discussed it on the surface, it's all part of the plan. Therefore, you haven't changed the plan, you've decided to use option 2 of the previously discussed plan.

[rjack321]

But to me, if you're going to change your plan on the fly, you'd better have discussed it on the surface, and, if you've discussed it on the surface, it's all part of the plan. Therefore, you haven't changed the plan, you've decided to use option 2 of the previously discussed plan.

By most people's concept we <barely> plan on the surface. Mostly rock bottom and maximum planned deco. Then again we're diving in the ~1.1-1.2 range on the bottom so there's tons of wiggle room on the MOD and its really not a limiting factor.

I haven't done a deco dive right up to a 1.4 MOD of my backgas ever. Recreationally I have stopped a few dives on EAN32 at 110ft. Partly that's a ppO2 issue, partly because that's where I draw the line on END. Most EAN32 dives don't even hit 100ft, the 110footers are unusual coincidences.

[LiteHedded]

I still haven't heard any reasons. the silence speaks pretty loudly

[muddiver]

Now, you tell me that 1.6 is an "Industry Standard" because someone published it in a book somewhere, my friend Ian had to get a certification card to do something he's been doing since before there were certification cards for it, and I'm making a stupid decision because I'm following the standards of the time I was trained. PADI issues C-Cards to divers diving voodoo gas without requiring them to make a dive using the gas.

I'm all for learning from mistakes. One of the problems with the industry is that folks make up "industry standards" with no basis for them. We've determined in this thread that some divers are more susceptible to ox-tox than others, some can tox at PO2's of 1.2 or less, and that some of us aren't as prone to suffering from ill effects of O2 than others. What are these industry standards supposed to do? Keep us safe? DIVING ISN'T SAFE, AND ANYONE WHO TELLS YOU IT IS IS BLOWING SMOKE UP YOUR ASS. Diving is a sport that carries some risk. It is up to each of us to define what level of risk we are willing to accept to accomplish our goals. When someone dies in the #3 pumproom of the Spiegel Grove, I don't say to myself "What an idiot!", I say "well, he tooks his chances and paid the price". I don't penetrate caves or wrecks because it's OUT OF MY COMFORT ZONE. I don't think that people who do are stupid, I just don't do it myself.

Humm...

The latest U.S.N. Diving Manual states in Chapter 10 Nitrogen-Oxygen Diving Operations, that dives with a PO2 beyond 1.4 are not permitted. It is also stated that CNS toxicity is usually not encountered unless the partial pressure of oxygen approaches or exceeds 1.6.

Yep, I'm pretty sure the Navy printed that up without doing any research. ;)

[Jax]

Humm...

The latest U.S.N. Diving Manual states in Chapter 10 Nitrogen-Oxygen Diving Operations, that dives with a PO2 beyond 1.4 are not permitted. It is also stated that CNS toxicity is usually not encountered unless the partial pressure of oxygen approaches or exceeds 1.6.

Yep, I'm pretty sure the Navy printed that up without doing any research. ;)

Is that the same Navy that used to say 1.6 and 2.0 was okay? (So sayeth a Navy Captain.)

[muddiver]

Is that the same Navy that used to say 1.6 and 2.0 was okay? (So sayeth a Navy Captain.)

Diving physiology is linked to medicine and our veague understanding of human physiology. Someone once made a wise statement that medicine is not an exact science. Therefore, diving physiology, on which decompression theory and the effects of breathing gases on the human body are based, is probably also not an exact science so there will be changes occationally based on our experiences with the occurances of OxTox, Nitrogen Narcosis, HPNS, etc.

The U.S.N. Diving Manual has not been updated since 2005 so with revision 6 I would think there would be some changes. Funny how they fit the standards of some of the recreational diving training agencies.

[ajduplessis]

Alright, I'm an NDL diver who would push a gentle 1.8 max depth for the right reason(s). My non-deco IANTD Nitrox training was 1.6/1.8. Still a 3 minute SS and tank price unchanged.

I would love to see the IANTD nitrox manual suggesting/teaching PPO of 1.8

PPO2 1.6 MAX on recreational dives (Warm water and low workload )!!!!

[Pullmyfinger]

I'd like to see it as well. It's possible he's just going on memory and thinks it's 1.8.
I'd double check that.
How old is that IANTD manual?

-Mitch

[Tortuga68]

I still haven't heard any reasons

At the end of the day, there's really only one reason for exceeding a particular PPO2 benchmark - whether it's 1.6, 1.4, 1.2 or whatever: that you believe that the risk of an incident occuring to you on the particular dive that you are doing is acceptable

I certainly don't do it because I'm too tight to buy a drysuit (so I can dive in 30 degree C water? yeah, right) or whatever your other blanket hypothethis was, cutting deco time?

What do I base my risk assessment on?

1. Dosage/exposure theory
2. Personal history/circumstances
3. Buddy experience
4. Various other factors

YMMV

[LiteHedded]

At the end of the day, there's really only one reason for exceeding a particular PPO2 benchmark - whether it's 1.6, 1.4, 1.2 or whatever: that you believe that the risk of an incident occuring to you on the particular dive that you are doing is acceptable

I certainly don't do it because I'm too tight to buy a drysuit (so I can dive in 30 degree C water? yeah, right) or whatever your other blanket hypothethis was, cutting deco time?

What do I base my risk assessment on?

1. Dosage/exposure theory
2. Personal history/circumstances
3. Buddy experience
4. Various other factors

YMMV

or a 2.31? can you not get hypoxic gas? is that why you want to push it like that?

[Tortuga68]

The point is no matter what your limit is, there is likely going to be someone somewhere who is more conservative than you. What's acceptable to you might seem foolhardy to others, whether it's cave diving, deep air or whatever. I'm okay with that, everyone's entitled to their opinion.

To answer your question, hypoxic gas is available where I do my deep dives, although I'm not certified for it - but there's nothing stopping me getting certified if I felt the need to do so. Nothing to do with saving money, nickel rocketry, deco weenery or anything else other than I don't feel the need for it currently

I know you're not going to agree with me, but that's life. I'm sure if I do oxtox you'll be clucking your tongue and saying I told you so, but I won't be around to be bothered by it, so be my guest

If you feel that's promoting unsafe diving practices to Johnny Scubaboard, so be it - I disagree. When I tell people not to do it, I get told I'm "thumbing my nose" at the general populace. Since lying or not expressing my personal viewpoint when it's solicited are both equally unpallatable to me, tough

For me, it's a challenge to gradually push what I consider to be reasonably acceptable (to me) limits. I've gradually worked my way down to 2.0 and feel okay doing it. I know other people who have done 2.31 and more, and I believe I can do it too, with what I consider an acceptable degree of risk - not that there's any peer pressure for me to do it, because there isn't. It's just a personal thing

Neither would I encourage anyone else to do it, especially without appropriate experience & consideration

[LiteHedded]

The point is no matter what your limit is, there is likely going to be someone somewhere who is more conservative than you. What's acceptable to you might seem foolhardy to others, whether it's cave diving, deep air or whatever. I'm okay with that, everyone's entitled to their opinion.

To answer your question, hypoxic gas is available where I do my deep dives, although I'm not certified for it - but there's nothing stopping me getting certified if I felt the need to do so. Nothing to do with saving money, nickel rocketry, deco weenery or anything else other than I don't feel the need for it currently

I know you're not going to agree with me, but that's life. I'm sure if I do oxtox you'll be clucking your tongue and saying I told you so, but I won't be around to be bothered by it, so be my guest

If you feel that's promoting unsafe diving practices to Johnny Scubaboard, so be it - I disagree. When I tell people not to do it, I get told I'm "thumbing my nose" at the general populace. Since lying or not expressing my personal viewpoint when it's solicited are both equally unpallatable to me, tough

For me, it's a challenge to gradually push what I consider to be reasonably acceptable (to me) limits. I've gradually worked my way down to 2.0 and feel okay doing it. I know other people who have done 2.31 and more, and I believe I can do it too - not that there's any peer pressure for me to do it, there isn't. It's a personal thing

Neither would I encourage anyone else to do it, especially without appropriate experience & consideration

well, no. I hope you get some symptoms before you have a seizure. and I hope it's not someone reading this that it happens to.

I wonder if the guy who toxed at Wayne's World over in Tampa got any symptoms before he toxed and drowned. or the guy AG had to rescue during a class of his. or the lady who toxed at The Crack (a river cave) while diving a pretty 'normal' ppo2. there's a reason the standard gas around here is 32% instead of the 34% it used to be. I'll give you a hint: it's because of dead people.

I just question what advantage comes along with adding SUBSTANTIAL risk to your dive profile. not having to take a class?

[Tortuga68]

well, no. I hope you get some symptoms before you have a seizure. and I hope it's not someone reading this that it happens to

Well, we agree that neither of us wants for me or anyone else to oxtox. What a breakthrough, this could be the start of a beautiful friendship <3



I wonder if the guy who toxed at Wayne's World over in Tampa got any symptoms before he toxed and drowned. or the guy AG had to rescue during a class of his. or the lady who toxed at The Crack (a river cave) while diving a pretty 'normal' ppo2. there's a reason the standard gas around here is 32% instead of the 34% it used to be. I'll give you a hint: it's because of dead people

Yes, I wonder. People die all the time. So what? A sample size of three is extremely low. Shall we list all the people that have done >1.6 and lived? The A&I forum is full of people who died doing 'normal' dives

Anyway, what was the "pretty normal" PP02 of the Crack lady in question? As was mentioned earlier, people have toxed at and below 1.6, does that mean everyone should dive 1.0? I'm really not sure what your point is

I don't see what standard mix has to do with it either, .32 has a different MOD to .34 no matter what your PP02 limit is... Are you saying that .32 is safer at >insert PP02 here< than .34 is at the same partial pressure?



I just question what advantage comes along with adding SUBSTANTIAL risk to your dive profile. not having to take a class?

You asked for reasons to exceed what you consider to be a safe limit, not advantages. I gave you my reasons. As I already said, taking the class is not a factor. Let's all not dive then no-one will oxtox. It's a personal risk assesment based on factors I have already detailed. You feel you're safe at 1.6, other people have higher or lower limits. Not everyone shares your opinion when it comes to their own diving habits. Let it go

[LiteHedded]

Well, we agree that neither of us wants for me or anyone else to oxtox. What a breakthrough, this could be the start of a beautiful friendship <3




Yes, I wonder. People die all the time. So what? A sample size of three is extremely low. Shall we list all the people that have done >1.6 and lived? The A&I forum is full of people who died doing 'normal' dives

Anyway, what was the "pretty normal" PP02 of the Crack lady in question? As was mentioned earlier, people have toxed at and below 1.6, does that mean everyone should dive 1.0? I'm really not sure what your point is

I don't see what standard mix has to do with it either, .32 has a different MOD to .34 no matter what your PP02 limit is... Are you saying that .32 is safer at >insert PP02 here< than .34 is at the same partial pressure?




You asked for reasons to exceed what you consider to be a safe limit, not advantages. I gave you my reasons. As I already said, taking the class is not a factor. Let's all not dive then no-one will oxtox. It's a personal risk assesment based on factors I have already detailed. You feel you're safe at 1.6, other people have higher or lower limits. Not everyone shares your opinion when it comes to their own diving habits. Let it go

meh
ok

[John_B]

I know you're not going to agree with me, but that's life. I'm sure if I do oxtox you'll be clucking your tongue and saying I told you so, but I won't be around to be bothered by it, so be my guest
No, everyone will say to wait for the official report that will never be released. :eyebrow:

[String]

[QUOTE=Tortuga68;5629227
I don't see what standard mix has to do with it either, .32 has a different MOD to .34 no matter what your PP02 limit is... Are you saying that .32 is safer at >insert PP02 here< than .34 is at the same partial pressure?
[/QUOTE]

Following their argument they may as well just use air - its even "safer" as has an even lower pO2 for a given depth :)

[ZenDiver.3D]

My usual- Above 45 meters- 1.4, below 45 meters- 1.2, and deco- 1.6.

That just seems to be the norm for me.

[Tortuga68]

Imagine if I posted that I was considering running a marathon...

- Don't you know you could have a heart attack and DIE??

- Why don't you drive instead, it would be quicker and easier & less risk of a heart attack

- Don't they have cars where you are? Or are you just too cheap to buy one?

[LiteHedded]

I get it. you're a big macho deep air, 'extended range', high ppo2 diving badass. you can pull it off because your RAW POWER allows you to tolerate levels of dumb that would kill mere mortals

http://2.bp.blogspot.com/_nGIOYZ-On2M/TAVr9UfhqfI/AAAAAAAAADw/Bsu2Zd2dncI/s400/AWESOME.jpg

[Tortuga68]

You're a big macho deep air, 'extended range', high ppo2 diving badass. you can pull it off because your RAW POWER allows you to tolerate levels of dumb that would kill mere mortals

Yeah, that's exactly what I'm saying :rolleyes:

And here's my t-shirt:

http://www.scubaboard.com/forums/attachment.php?attachmentid=86629&stc=1&d=1292421834

[LiteHedded]

lol ok
for real this time

[Tortuga68]

for real this time

http://www.scubaboard.com/forums/attachment.php?attachmentid=86630&stc=1&d=1292422610

[JahJahwarrior]

Hasn't the Navy done tests to determine the Po2 that killed the least people? I haven't studied this extensively but that's my understanding. For that reason, I trust that 1.4 working and 1.6 deco is the most Po2 I want for my own personal safety.

I have pushed it before, I think to 1.5 working but it might have been 1.6, I don't recall. I didn't stay at that depth for long, and I did not relish the idea of pushing it. I also switched to o2 once at 30' without thinking about it. I realized my mistake almost immediately and switched back, and now I'm extremely careful to double check my depth and my MOD before switching.

Because oxtox can be unpredictable, I see no sense at all in pushing my Po2 as any sort of personal challenge. I believe in taking predictable risks that are controllable. Messing around with gasses is not nearly as predictable or controllable as something like diving in a cave. The body's responses to gases can change based on a variety of factors beyond my direct control. I don't see any benefit to pushing Po2, diving with a high Po2 doesn't make me feel any better about myself when I go to bed at night, so I'll try to lower my Po2 risks and enjoy taking other, calculated risks.

[Tortuga68]

Thanks JJ for your well-worded post


Because oxtox can be unpredictable, I see no sense at all in pushing my Po2 as any sort of personal challenge

It's dealing with narcosis that interests me more as a personal challenge, not the PP02; that's just a by-product



Hasn't the Navy done tests to determine the Po2 that killed the least people?

That would be 0.0

[ScubaFeenD]

Thanks JJ for your well-worded post



It's dealing with narcosis that interests me more as a personal challenge, not the PP02; that's just a by-product

I understand that. I drive drunk as a personal challenge, the high blood-alcohol level is just a by-product. :D

[JahJahwarrior]

I don't understand the desire to deal with narcosis either. Do you also like to see how well you can drive while drunk? Seems very similar. Diving is an environment where mistakes kill you rather easily, similar to driving, and narcosis is very similar to drinking. Why take any more narcosis than necessary? Why drive if you are over the legal limit, or any limit that impairs you enough to make you dangerous to yourself or others?

[JahJahwarrior]

Thanks JJ for your well-worded post



It's dealing with narcosis that interests me more as a personal challenge, not the PP02; that's just a by-product




That would be 0.0

0 oxygen kills everyone....I think you meant .21.

[Tortuga68]

I don't understand the desire to deal with narcosis either. Do you also like to see how well you can drive while drunk? Seems very similar. Diving is an environment where mistakes kill you rather easily, similar to driving, and narcosis is very similar to drinking. Why take any more narcosis than necessary? Why drive if you are over the legal limit, or any limit that impairs you enough to make you dangerous to yourself or others?

I'll agree with "narcosis is very similar to drinking" in that it impairs your motor and mental skills, but I think that like most analogies, the comparison of drink-driving to diving narcosis fails to hold true under closer examination

People love to play the drink-driving card; it's an emotive one that most people can relate to, usually with negative connotations - it's illegal for a start, and in Western society at least we've all been bombarded with public awareness campaigns about how evil it is and the harm it does to innocent people, families, society etc

However for the sake of conversation, let's adopt your analogy: what is the 'safe' blood alcohol content for driving? 0.00? 0.02? 0.05? 0.08? 0.10? They are all legal in various parts of the world, so which one should be applied as a blanket rule for everyone? 0.00 is the safest, right? But would there be no motor vehicle accidents if everyone was at 0.00? No

Some people are unsafe to drive at 0.0x, the same as some people get narc'd out of their brain at XXm. No I am not saying, as LiteHedded said, that I am 'better' than anyone else - just that different people have different tolerances, and experiences

Do you see a similarity with some comments this thread?

[Tortuga68]

0 oxygen kills everyone....I think you meant .21

Yes you're right; although sometimes everyone dying doesn't seem like such a bad idea when it comes to threads like this one

[JahJahwarrior]

I agree that people's impairment under different po2's and bac's will vary. However in both cases we have impairment that is difficult or impossible for the impaired person to measure, and a situation where death risk is increased due to impairment, with some base level of death risk inherent in the sport.

Everyone has to set limits foe themselves. I feel the analogy is near perfect, aside from the fact that driving impaired has a higher chance of killing others than diving impaired.

[Tortuga68]

1. I agree that people's impairment under different po2's and bac's will vary. However in both cases we have impairment that is difficult or impossible for the impaired person to measure, and a situation where death risk is increased due to impairment, with some base level of death risk inherent in the sport.

2. Everyone has to set limits for themselves. I feel the analogy is near perfect, aside from the fact that driving impaired has a higher chance of killing others than diving impaired.

Well here's my opinion, which is just that, an opinion & therefore valid for me only:

1. I don't like arguing this one because again it is an emotive issue, but when I was a teenager I could get wasted on 4 beers; now I could have 4 beers and do most things competently. What does that mean in terms of diving? Nothing

2. Another difference to the analogy is that if you are narc'd you can ascend and become 'instantly' sober; of course you have know to do it, but you can't do that when you're drunk either way

We're way off topic as usual - PPO2 1.6 is a safe guideline, and I support it. Most people aren't going to die if they exceed it, otherwise the safe guideline would be lower. Likewise most people - but not all - will be safe slightly above it. Would everyone be safer if the 'limit' was 1.4 or 1.2?

Guess that that means? Someone will go beyond 1.6 and live; and someone will stay under it and die

[LiteHedded]

Well here's my opinion, which is just that, an opinion & valid for me only:

1. I don't like arguing this one because again it is an emotive issue, but when I was a teenager I could get wasted on 4 beers; now I could have 4 beers and do most things competently. What does that mean in terms of diving? Nothing

2. Another difference to the analogy is that if you are narc'd you can ascend and become 'instantly' sober; of course you have know to do it, but you can't do that when you're drunk either way

We're way off topic as usual - PPO2 1.6 is a safe guideline, and I suport it. Most people aren't going to die if they exceed it, otherwise the safe guideline would be lower. Likewise most people - but not all - will be safe slightly above it

Guess that that means? Someone will go beyond 1.6 and live; and someone will stay under it and die

assuming you are able to ascend...

[Tortuga68]

What part of "of course you have to know to do it" don't you get?

It's still a difference in the analogy - you can't 'ascend' when you're drunk

[LiteHedded]

What part of "of course you have to know to do it" don't you get?

It's still a difference in the analogy - you can't 'ascend' when you're drunk

the point being, even if you know how to do it you're not always able to ascend in technical diving...

[Tortuga68]

Indeed. As I said earlier, I am comfortable diving >1.6 for the dives that I do

Which happen to be OW dives, so ascending is always an option

Again, I'm not suggesting (or promoting, as you said) that other people should do PPO2 >1.6

Doesn't mean I'm a superdiver on nickel rocketry

Ascending to 30m is always an option for me

[Kevin Carlisle]

Indeed. As I said earlier, I am comfortable diving >1.6 for the dives that I do

Which happen to be OW dives, so ascending is always an option

Again, I'm not suggesting (or promoting, as you said) that other people should do PPO2 >1.6

Doesn't mean I'm a superdiver on nickel rocketry

Ascending to 30m is always an option for me

He is talking about OW, in technical diving there is a term virtual overhead. Yes you may go up, but going up can kill you. If you dont know this you might want to learn about it.

[JahJahwarrior]

What is the probability that you will recognize when you are impaired?

How many people are astounded at their impairment when they see a video of their drunken behavior later, when sober?

Is there any benefit to diving with a high po2 or high pn2, aside from beating your chest on forums, in dive shops, or while drinking with your buddies?

[Tortuga68]

He is talking about OW, in technical diving there is a term virtual overhead. Yes you may go up, but going up can kill you. If you dont know this you might want to learn about it.

What, I can't go straight up from 85m to 0m? Please tell me more, I'm new to this diving caper and I want to learn about it

[LiteHedded]

What, I can't go straight up from 85m to 0m? Please tell me more, I'm new to this diving caper and I want to learn about it

they teach you this stuff in proper technical diving classes.

ascending is almost always the wrong move. the deep deco is the last thing I would want to blow off. the bubbles you create down there will feel really nice on the surface.

but with the narcosis and the ppo2 you're dealing with being bent like a pretzel is probably lower on the list of concerns

[NetDoc]

Snarky posts removed.
Dial it down a notch.

[peterbj7]

Damn, I missed them!

[Tortuga68]

they teach you this stuff in proper technical diving classes

What, like decompression procedures?



ascending is almost always the wrong move

I tried not ascending but found I ran out of air eventually

[rjack321]

Jeesh guys slow day or do you always feed the trolls??
http://www.scubaboard.com/forums/technical-diving-specialties/297905-psai-narcosis-management-course-73m-air.html

[Tortuga68]

Don't blame me. all I did was answer John's question honestly

[halemanō]

I would love to see the IANTD nitrox manual suggesting/teaching PPO of 1.8

PPO2 1.6 MAX on recreational dives (Warm water and low workload )!!!!


I'd like to see it as well. It's possible he's just going on memory and thinks it's 1.8.
I'd double check that.
How old is that IANTD manual?

Last I new, Joe Dituri was living on Oahu and he may still have one of the old ones.

I got mine from the author, who I did my Advanced EANx Instructor crossover with; the founder, Instructor Trainer #1. My Instructor card is dated 09 June 2001 (#3611).

NITROX MANUAL: Complete Guide to Nitrox Diving
by Dick Rutkowski

1st Edition - Dec '89

Revised
Sept '90
Nov '93
Mar '94
Oct '96

Copyright '94 by H.I., Inc.

flipping fairly quickly through the pages; page 37, in Dalton's Law, top paragraph -

"...It must be determined what PO2 is being inhaled to avoid exceeding the safe physiological limits of oxygen and prevent CNS O2 toxisity. This amount of oxygen is 1.6 ATA/Bar (A) for 45 minutes. This will be explained in a later chapter."

page 40, still in Dalton's Law; most of the page is Figure 7, the
NOAA OXYGEN PARTIAL PRESSURE and EXPOSURE LIMITS for NITROGEN-OXYGEN MIXED GAS WORKING DIVES.

the top section is labeled "Normal Exposure Oxygen Partial Pressure Limits" with single duration and 24-hour duration times for 1.6-0.6, in one tenth increments.

the bottom section is labeled "Exceptional Exposure Limits" with single duration times for 2.0-1.3, in one tenth increments.

if you are still following along, those limits are; 30, 45, 60, 75, 120, 150, 180, 240. The cliff note are that; 2.0 has an Exceptional Limit of 30 minutes, 1.6 has an Exceptional Limit of 120 minutes, 1.3 has an Exceptional Limit of 240 minutes.

three paragraphs later, this is the entire paragraph -

"Exceptional Exposure Limits are for use only in lifesaving operations."

page 45 starts the PHYSIOLOGICAL IMPLICATIONS OF OXYGEN AND OXYGEN LIFE SUPPORT RANGES.

3rd paragraph -

"For normal diving operations, oxygen partial pressures must be maintained between .016 and 1.6 ATA/Bar (A). During oxygen decompression and recompression therapy, higher levels of oxygen can be tolerated. Under these circumstances, divers are at rest and/or under controlled conditions in a recompression chamber. EXCERCISE GREATLY REDUCES A DIVER'S TOLERANCE TO OXYGEN. Oxygen levels above 1.6 ATA/Bar (A) should not be used during a normal dive."

page 46 is titled Oxygen Limits for Life Support Systems. Near the bottom is an "example" table for ATA's 1, 2, 3, 4, 4.5, 5, 6, 7.6, where 7.6 on AIR is 218 fsw and PO2 1.6 with an *. Higher up in the "example" table 5 ATA / 132 fsw is 1.6* for NNI and 4.5 / 114 is 1.6* for NNII.

At the bottom of the page is; "*1.6 ATA/Bar (A) O2 limit for a working diver" I underlined that last bit; all other emphasis is the way it is in the book.

page 47, once again most of the page is Figure 7, the
NOAA OXYGEN PARTIAL PRESSURE and EXPOSURE LIMITS for NITROGEN-OXYGEN MIXED GAS WORKING DIVES, again with the "Exceptional Exposure Limits"

now skipping to the back of the book

Appendix E, Table E-2 is the NOAA NITROX I DECOMPRESSION TABLE (32%) -

I am tiring of this transposing, but I will just give the info for a 20 minute dive to 150fsw; 4:40 ascent time to first stop at 10fsw, 4 minute stop, repetitive group H.

Appendix F, Table F-2 is the NOAA NITROX II DECOMPRESSION TABLE (36%) -

a 30 minute dive to 120fsw; 3:40 ascent time to 3 minute 10fsw stop. There is no repetitive group as repetitive dives are not allowed after 36% exceptional exposure dives.

My crossover was a "one on one" few days with Hyper Dick. He read between the lines for me. He told me that with my significant major joint/bone injury history (compound fractured right wrist, shattered right patella, seriously broken right elbow & titanium reinforced tibia, completely rebuilt right shoulder, un-repaired right hip injured in most of those different incidents) I should not consider deco diving. He said that given my prowess in the water, gently gliding down to the props of the Duane for a pic of a Bull Shark or Goliath Grouper on 36% was something I could consider. Just no chasing! :dontknow:

[LiteHedded]

What, like decompression procedures?




I tried not ascending but found I ran out of air eventually

you posted earlier that the solution to your problem was to ascend to 30m. that's what I'm referencing. it's a good way to get yourself paralyzed. is that what they taught you in your deep air class? perhaps deco procedures?

[ScubaFeenD]

Clearly, he has some reason for disregarding obvious risk. So no point in arguing about it anymore; he accepts that it is high and Tortuga doesn't care. So, how bout tortuga just let people he is diving with know so when he eventually does seize, no one is silly enough to try and save his a$$ at risk to themselves. I have heard of people risking personal safety to try and save a toxing diver. If a toxing diver is hit after diving within generally accepted risk limits then a rescue should be attempted, if not then there is no need for two victims--personally i care much less about this idiot in this scenario.

Really i dont care if someone makes a decision that will kill them, as long as it doesn't effect someone else.

[Kevin Carlisle]

Clearly, he has some reason for disregarding obvious risk. So no point in arguing about it anymore; he accepts that it is high and Tortuga doesn't care. So, how bout tortuga just let people he is diving with know so when he eventually does seize, no one is silly enough to try and save his a$$ at risk to themselves. I have heard of people risking personal safety to try and save a toxing diver. If a toxing diver is hit after diving within generally accepted risk limits then a rescue should be attempted, if not then there is no need for two victims--personally i care much less about this idiot in this scenario.

Really i dont care if someone makes a decision that will kill them, as long as it doesn't effect someone else.

I know someone that was with a diver who toxed. It wont last but a few seconds then its all over so he wont be a danger to anyone.

[ScubaFeenD]

I know someone that was with a diver who toxed. It wont last but a few seconds then its all over so he wont be a danger to anyone.

Is every toxing incident the same? I haven't read that anywhere.

[Kevin Carlisle]

Is every toxing incident the same? I haven't read that anywhere.

Oh well i am soo sorry.

[ScubaFeenD]

Oh well i am soo sorry.

You're so helpful dr Carlisle.

[ajduplessis]

Last I new, Joe Dituri was living on Oahu and he may still have one of the old ones.

I got mine from the author, who I did my Advanced EANx Instructor crossover with; the founder, Instructor Trainer #1. My Instructor card is dated 09 June 2001 (#3611).

NITROX MANUAL: Complete Guide to Nitrox Diving
by Dick Rutkowski

1st Edition - Dec '89

Revised
Sept '90
Nov '93
Mar '94
Oct '96

Copyright '94 by H.I., Inc.

flipping fairly quickly through the pages; page 37, in Dalton's Law, top paragraph -

"...It must be determined what PO2 is being inhaled to avoid exceeding the safe physiological limits of oxygen and prevent CNS O2 toxisity. This amount of oxygen is 1.6 ATA/Bar (A) for 45 minutes. This will be explained in a later chapter."

page 40, still in Dalton's Law; most of the page is Figure 7, the
NOAA OXYGEN PARTIAL PRESSURE and EXPOSURE LIMITS for NITROGEN-OXYGEN MIXED GAS WORKING DIVES.

the top section is labeled "Normal Exposure Oxygen Partial Pressure Limits" with single duration and 24-hour duration times for 1.6-0.6, in one tenth increments.

the bottom section is labeled "Exceptional Exposure Limits" with single duration times for 2.0-1.3, in one tenth increments.

if you are still following along, those limits are; 30, 45, 60, 75, 120, 150, 180, 240. The cliff note are that; 2.0 has an Exceptional Limit of 30 minutes, 1.6 has an Exceptional Limit of 120 minutes, 1.3 has an Exceptional Limit of 240 minutes.

three paragraphs later, this is the entire paragraph -

"Exceptional Exposure Limits are for use only in lifesaving operations."

page 45 starts the PHYSIOLOGICAL IMPLICATIONS OF OXYGEN AND OXYGEN LIFE SUPPORT RANGES.

3rd paragraph -

"For normal diving operations, oxygen partial pressures must be maintained between .016 and 1.6 ATA/Bar (A). During oxygen decompression and recompression therapy, higher levels of oxygen can be tolerated. Under these circumstances, divers are at rest and/or under controlled conditions in a recompression chamber. EXCERCISE GREATLY REDUCES A DIVER'S TOLERANCE TO OXYGEN. Oxygen levels above 1.6 ATA/Bar (A) should not be used during a normal dive."

page 46 is titled Oxygen Limits for Life Support Systems. Near the bottom is an "example" table for ATA's 1, 2, 3, 4, 4.5, 5, 6, 7.6, where 7.6 on AIR is 218 fsw and PO2 1.6 with an *. Higher up in the "example" table 5 ATA / 132 fsw is 1.6* for NNI and 4.5 / 114 is 1.6* for NNII.

At the bottom of the page is; "*1.6 ATA/Bar (A) O2 limit for a working diver" I underlined that last bit; all other emphasis is the way it is in the book.

page 47, once again most of the page is Figure 7, the
NOAA OXYGEN PARTIAL PRESSURE and EXPOSURE LIMITS for NITROGEN-OXYGEN MIXED GAS WORKING DIVES, again with the "Exceptional Exposure Limits"

now skipping to the back of the book

Appendix E, Table E-2 is the NOAA NITROX I DECOMPRESSION TABLE (32%) -

I am tiring of this transposing, but I will just give the info for a 20 minute dive to 150fsw; 4:40 ascent time to first stop at 10fsw, 4 minute stop, repetitive group H.

Appendix F, Table F-2 is the NOAA NITROX II DECOMPRESSION TABLE (36%) -

a 30 minute dive to 120fsw; 3:40 ascent time to 3 minute 10fsw stop. There is no repetitive group as repetitive dives are not allowed after 36% exceptional exposure dives.

My crossover was a "one on one" few days with Hyper Dick. He read between the lines for me. He told me that with my significant major joint/bone injury history (compound fractured right wrist, shattered right patella, seriously broken right elbow & titanium reinforced tibia, completely rebuilt right shoulder, un-repaired right hip injured in most of those different incidents) I should not consider deco diving. He said that given my prowess in the water, gently gliding down to the props of the Duane for a pic of a Bull Shark or Goliath Grouper on 36% was something I could consider. Just no chasing! :dontknow:

Thanks for your input, great reading. Hope you don't mind quoting some of your input.

"...It must be determined what PO2 is being inhaled to avoid exceeding the safe physiological limits of oxygen and prevent CNS O2 toxisity. This amount of oxygen is 1.6 ATA/Bar (A) for 45 minutes. This will be explained in a later chapter."

"For normal diving operations, oxygen partial pressures must be maintained between .016 and 1.6 ATA/Bar (A)."


"Exceptional Exposure Limits are for use only in lifesaving operations."


Are we then in agreement that 1.6 is what is accepted and recommended by IANTD for diving and not 1.8?

[padiscubapro]

Thanks for your input, great reading. Hope you don't mind quoting some of your input.

"...It must be determined what PO2 is being inhaled to avoid exceeding the safe physiological limits of oxygen and prevent CNS O2 toxisity. This amount of oxygen is 1.6 ATA/Bar (A) for 45 minutes. This will be explained in a later chapter."

"For normal diving operations, oxygen partial pressures must be maintained between .016 and 1.6 ATA/Bar (A)."


"Exceptional Exposure Limits are for use only in lifesaving operations."


Are we then in agreement that 1.6 is what is accepted and recommended by IANTD for diving and not 1.8?


I have one of the early manuals (if I remember it says IAND on it) , not sure what edition I'll have to did it up... But I started diving Nitrox around 91 and we used 1.6 as our bottom WORKING gas and up to 1.8 or 1.9 for deco..

[halemanō]

Are we then in agreement that 1.6 is what is accepted and recommended by IANTD for diving and not 1.8?

First, I will quote my original statement that you used to start this line of discussion;


Alright, I'm an NDL diver who would push a gentle 1.8 max depth for the right reason(s). My non-deco IANTD Nitrox training was 1.6/1.8. Still a 3 minute SS and tank price unchanged.

In the weeks leading up to my personal, one-on-one training from Hyper Dick I was trained as both a PADI Enriched Air Diver and a PADI Enriched Air Specialty Instructor. The classroom for those training sessions is the room directly adjacent to the Hyperbarics International, Incorporated training room, and both of those training's also included a visit to said H.I., Inc. training room, with Dick doing some of the training.

This was 4.5 years after the last revision of the IANTD Manual we used during my IANDT Instructor crossover. It is very, very likely that Dick was consulted by PADI with regards to the wording of the PADI Enriched Air Diver Manual, even if not in person, and there is no doubt that Dick knew the wording used in the PADI Manual; mine is a 1st edition, 1995.


The contingency oxygen partial pressure limit is 1.6 ata. Dives beyond this limit have the potential for immediate oxygen toxicity. The partial pressures between 1.4 and 1.6 ata. should be considered as a margin for error only. .....

Training manuals go through a vetting process, which I'm assuming include insurance and attorney input. That results in them being written for the "lowest common denominator." With regards to NAVY training that is still a pretty in shape 20 something year old "killer." NOAA's LCD is still an experienced "research diver." The first IANDT Manuals were perhaps not "dumbed down" enough for the typical beginning OW diver, but Dick knew I was well within the target of the Manual he trained me with.

If one is limiting the dives to 1.6 ata for the working portion of the dive, in the terminology being used in 2001, what is the "contingency" ata? For non-deco diving, using terminology similar to PADI, is it so unreasonable for Dick and I to call 1.8 the "contingency" ata? If I am not "working," just making a short foray below 1.6 to rest gently on the bottom to take a picture, are you saying that I still "must" consider myself to be working?

A couple weeks before my crossover, I made a dive on the Bibb with a 28% mix that my fellow PADI Instructor buddy and I blended ourselves. The picture below was at a depth of 137 fsw. As we were only PADI nitrox trained, that is the reason for the custom blend.


http://www.scubaboard.com/gallery/data/500/BibbJew_137ft.jpg (http://www.scubaboard.com/gallery/showphoto.php/photo/89117)

After taking that pic, I turned to find the entire visiting TDI Nitrox class and Instructor (that I knew were on 32%) waiting for their turn. Back on the boat I asked some questions and learned that TDI training had different max and contingency limits than PADI training. :dontknow:

As an Instructor, I teach to Standards. IANTD has revised their Standards so if I were to teach any IANTD EANx courses I would of course use current Standards. That does not mean that for my personal diving I feel the need to treat myself as a "lowest common denominator."

Please do not take my own personal diving limits as me saying you should not consider yourself as one of the "lowest common denominators." :kiss2:

[Tortuga68]

you posted earlier that the solution to your problem was to ascend to 30m. that's what I'm referencing. it's a good way to get yourself paralyzed

Apparently it's not a good way, since I remain free of paralysis



is that what they taught you in your deep air class? perhaps deco procedures?

If you cut the run time on Decoplanner, the first stop is at 30m /shrugs



how bout tortuga just let people he is diving with know so when he eventually does seize, no one is silly enough to try and save his a$$ at risk to themselves

I don't know what makes you think they don't know that already. Thanks for your humanitarian concern though

[TraceMalin]

A recent discussion in another thread highlighted the difference of opinions among divers on an acceptable PO2 for gas planning. Over the years, I've seen a shift in the recommended max PO2.

I'm a bit curious about the difference in personal attitudes and training on the limits that people use in planning the working portion and deco portion of their dives.

For working portion, do you normally prefer 1.0 or less, 1.2, 1.4, 1.6, or something else?

For the deco portion of your dives do you normally prefer to keep your PO2 at 1.4, 1.6, or something else?

What adjustments (if any) do you make for adverse conditions? (strong current, cold water, etc.)

What is the main driving force in your choices?

Hyperoxic mixes 1.2 - 1.3
Normoxic mixes 1.4
Air 1.4
Deco 1.6

I seem to be more sensitive to oxygen in hyperoxic mixtures in cold water and current.

[Kern]

Hyperoxic mixes 1.2 - 1.3
Normoxic mixes 1.4
Air 1.4
Deco 1.6

I seem to be more sensitive to oxygen in hyperoxic mixtures in cold water and current.

Do you not teach PSAI's signiture, narcosis management course at all? Or do you just not teach beyond a level that would increase you ppO2 above 1.4? Or do you go somewhere with low current & warm water & exceed ppO2 1.4?

[TraceMalin]

Do you not teach PSAI's signiture, narcosis management course at all? Or do you just not teach beyond a level that would increase you ppO2 above 1.4? Or do you go somewhere with low current & warm water & exceed ppO2 1.4?

No, I do not teach the PSAI narcosis management program.

[nhebrant]

1.4 working (although i have gone to 1.6 no probs) and 1.6 for deco.....
All depends on your body what can be tolerated. BSAC allows up to 1.8 I believe....

3.0 is where everyone will convulse, below that just depends on what you can tolerate and how you feel. Although said that Im pretty sure that recreational dive computers (suunto and mares for eg) do not allow anything above 1.6.

rgds

[String]

All depends on your body what can be tolerated. BSAC allows up to 1.8 I believe....

No, BSAC are 1.4 although they've fiddled it to fit their 35m qualfication and allow "32% nitrox to be dived to 35m meaning 1.44 for no-stop dives" just as a fudge. They only allow 1.6 deco at 6m so its 1.4 even for deco below that. They're the most conservative (ok, backward) i cant think of ignoring the world-wide norm.

[Tortuga68]

3.0 is where everyone will convulse

What are you basing that statement on?

[peterbj7]

I don't know that that's true, but I am told by a nurse that 3.0 is the highest they use in pressure chambers in hospitals, at any rate in the UK. At that level they strictly restrict exposure to reduce the likelihood of convulsions, which although not lethal are pretty discomfiting for the patient.

I also believe that in wartime missions were planned with the pO2 going up as far as 3.0, even though in peacetime exposure was limited to 2.0.

[kanonfodr]

I also believe that in wartime missions were planned with the pO2 going up as far as 3.0, even though in peacetime exposure was limited to 2.0.

I highly doubt that missions are ever planned to hit a PO2 of 3, it is likely only a contingency since most units performing underwater ops of a combat nature don't like being risky with the things they can control. Getting above 2.0 is probably one of those risks, no need to risk someone dying before you even met the enemy. But if the choice is either be discovered or momentarily go deep and jack up the PO2, they would most likely go deep and risk it.

Peace,
Greg

[FireInMyBones]

A recent discussion in another thread highlighted the difference of opinions among divers on an acceptable PO2 for gas planning. Over the years, I've seen a shift in the recommended max PO2.

I'm a bit curious about the difference in personal attitudes and training on the limits that people use in planning the working portion and deco portion of their dives.

For working portion, do you normally prefer 1.0 or less, 1.2, 1.4, 1.6, or something else?

For the deco portion of your dives do you normally prefer to keep your PO2 at 1.4, 1.6, or something else?

What adjustments (if any) do you make for adverse conditions? (strong current, cold water, etc.)

What is the main driving force in your choices?

When I first took Nitrox, I ran a 1.6 at all times. After tech training: 1.2 working, 1.4 deco gases (not O2), 1.6 for O2.

If it is a new dive or conditions are a little wild, I drop my working to no more than 1.0

[Tortuga68]

I highly doubt that missions are ever planned to hit a PO2 of 3, it is likely only a contingency...

There's a book Amazon.com: ABOVE US THE WAVES: The Story of Midget Submarines and Human Torpedoes (Pen & Sword Military Classics) (9781844154401): C E T Warren and James Benson: Books (http://www.amazon.com/ABOVE-US-WAVES-Submarines-Torpedoes/dp/1844154408/ref=sr_1_1?ie=UTF8&s=books&qid=1292823867&sr=1-1) which talks about the British 'Charioteers' and their missions; it's a good read

Before and in the early years of WW2 the Royal Navy exposure limits for 100% oxygen were 2 hours at 15m (PPO2=2.5) or 30 minutes at 27m (3.7). During the war, as a result of Kenneth Donald's research (spurred by the number of OT incidents), it was revised to 7.6m (1.76) with no time limit specified

Further research by the USN in the 1950s set a time limit for 7.6m of 65 minutes, with a maximum exceptional exposure limit of 14m (2.36) and 15 minutes. This wasn't revised until the 1970s

So yes missions were planned over 2.0 and no not everybody toxes when they hit 3.0