What is the deepest you have been on pure O2?

[lerpy]

"However, if you unluckily & catastrophically lose all your backgas at operational depth (and your buddy), and all you got is your 100% O2 Deco bottle -well you got no choice: switch to your deco bottle and immediately ascend "without physical exertion under heavy work of breathing" to a depth of 2 ATA, and do whatever deco time you can and/or ascend slowly to surface. There's a chance you may not OxTox seizure immediately (see Post #34 and especially #32 above). "

I feel like if this actually happened, and I made it out, I would seriously be re-assessing my gear, as well as my buddy. Possible consider just taking up reading or knitting.

 

[Diver0001]

So it seems like when Po2 is assumed to be 1.4 then MOD for pure oxygen is 13 feet but when we assume po2 of 1.6 then it is 20! A 7 foot deviation seems a bit too much so can anyone explain how deep can you be while you decompress on pure O2? Thanks.

Some of this depends on conditions, both in the water and of the physical condition of the diver, as well as (and this is important) the duration of the exposure. In chambers I think they often use fairly long exposures at 2.0, but then it's climate controlled and you won't drown if you tox.

Even if a some (or many?) people can tolerate higher pressures for a short time, you *are* underwater and from what I understand you can't easily predict the onset of a seizure. The best advice is to stick to the 1.4 recommendation.

R..

 

[Kevrumbo]

So it seems like when Po2 is assumed to be 1.4 then MOD for pure oxygen is 13 feet but when we assume po2 of 1.6 then it is 20! A 7 foot deviation seems a bit too much so can anyone explain how deep can you be while you decompress on pure O2? Thanks.

Some clarification of recommended, and commonly practiced nominal PPO2 parameters for Tech Deco Diving:

PPO2 for Bottom Mixes is 1.4 ATA MOD, and 1.2 ATA average for working operational depth.

PPO2 for Deco Mixes is 1.6 ATA MOD, and 1.2 ATA average over the stop depth ranges of an intermediate deco mix (i.g. deco stop depth range from 21m to 9m on Nitrox 50).

 

[nadwidny]

Hi Doppler, I understood Kevin as saying he starts off with a more liberal 30/85 setting to get out faster in the event of a contingent necessity. Then he adjust to a more conservative surfacing GF of 70 or 60 to extend his O2 stop as needed. It appears to be a sound strategy. The wildcard could be the O2 exposure but that depends on the dive profile.

I'm not sure I understand your question. Can you clarify?

Kevdumbo thinks he knows more than the experts and that's why he gets bent on a regular basis. Nobody is sure why you think that he is some sort of voice of authority on this.

 

[NAM001]

Based on your question I would recommend taking/ reading a advanced nitrox book. look at the calculations for otu and cns as to what happens to it at 1.4, 1.5, 1.6 1.7 1.8 atm. If yo have excel skills this will be easy for you to do. you will see that the big red line is at 1.6 and for what reason. applying a little buffer zone you will see why it is 1.4 for normal diving. Look at diving habits of new divers with poor depth control or attention to their depth period. This buffer allows some room for forgiving error when you cross the 1.4 line. When I started it was 1.8 to 2.0. some propose it be reduced to 1.2 or 1.3. Tech divers run much lower ppo2’s than rec divers be cause of the time involved in the associated dives. The routine rec diver should have no problems with 1.4 ppo2 as is current practice to use. DECO divers use the 1.6 limit. There are many reasons such as controlled stress from activity during deco stops that is not exercised while not in deco. The stops are usually not for long durations and the 1.6 is tolerable for those that can manage the use of it.

So it seems like when Po2 is assumed to be 1.4 then MOD for pure oxygen is 13 feet but when we assume po2 of 1.6 then it is 20! A 7 foot deviation seems a bit too much so can anyone explain how deep can you be while you decompress on pure O2? Thanks.

 

[Kevrumbo]

Kevdumbo thinks he knows more than the experts and that's why he gets bent on a regular basis. Nobody is sure why you think that he is some sort of voice of authority on this.

--Not claiming to be an expert . . .just relating experiences of adversity and overcoming it.

 

[SoFloDSO]

The basic recommendations depending on what training agency you go with are that you should not exceed 1.4pp for bottom mixes, and 1.6pp for deco mixes. The theory behind that is that you experience longer/higher pp exposures on bottom gases. Whereas you are generally ascending on deco gases with lessening exposure. Exposure to 1.6pp 100% O2 uses the common sense thinking that you are not going to be hanging out at 20 feet (the MOD is actually 19.8 feet) all day, but will instead be surfacing as soon as your deco time is up. That being said, the longer you stay at 19.8 feet on pure O2, the longer you are exposing yourself to the possibility of oxygen toxicity.

 

[Akimbo]

… That being said, the longer you stay at 19.8 feet on pure O2, the longer you are exposing yourself to the possibility of oxygen toxicity.

It is also worth pointing out that you are far more likely to suffer from Pulmonary Oxygen Toxicity (easily recovered symptoms) rather than CNS Oxygen Toxicity at these depths and durations.

http://www.scubaboard.com/forums/diving-medicine/440726-oxygen-toxicity-limits-symptoms.html