What's your PO2?

[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!

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..

 

[MauiScubaSteve]

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.

​

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.

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

 

[Trace Malinowski]

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.