o2pp 1.4ata+?

[grazie42]

Like a lot of others I´d not plan a dive for more than 1.4 for the "working" part and 1.6 for deco...

I might pop down to 1.6 without worrying to much but if nothing else, the incessant beeping of my computer, would convince me not to overstay my welcome...who said comps aren´t any good? ;-)

The only light I´d drop to 1.8 for would be my HID and even then I´d think before I did it...

For 120´ in Sweden I´d propably go for trimix (depending on the dive)
...somewhere nice and tropical I would use (and have used) air...

 

[Uncle Pug]

who said comps aren´t any good?

That would be me.

 

[Charlie99]

Would you bop down to 1.6 to get a picture?

Probably; on a low exertion dive.

Or 1.8 to get the light you dropped?

No. But I'll go to 2.0+ to get you or another diver in distress.

Or maybe you don't have a problem planning dives to 1.5.

I do have problems with greater than 1.3 for the bulk of the dive, but will go down to 1.6 for short period.

I believe in controlling my CNS clock instead of blindly looking at ONLY the ppO2.

Would you dive 32% to 120' (I have, and will)?

I did Devil's Throat in Cozumel on EAN31. If I had known in advance that it was going to be the 1st dive, I probably would have picked air, but EAN31 was acceptable since the time deep is very limited.

---------------------------------

What depth would YOU go on EAN36 to help a diver in distress???? (114' is about 1.6ppO2, ppO2 is 150'.)

Charlie Allen

 

[Simon L]

maybe i'm wrong (and I dont know any of you so this is NOT personal) but I'm picking up a bit of the 'deeper-longer-darker' vibe on this thread and its not that kind of subject.

OxTox will kill you. You will die. Its quite simple.

Do you want your headstone to read "Sadly missed by his Mum, Dad, Wife, Kids and a $500 torch."

Plan the dive, dive the plan. Plan for 1.4ppO2 and you have room to manouvre.

If you plan on dropping your torch, put a lanyard on it and take a reserve or two.

If you plan on looking at stuff (and taking pictures) at 130ft, design your mix for that depth.

Just my 02 (no pun intended!)

Si

 

[lundysd]

It seems as though my previous question was misinterpreted -- I know there are preliminary signs before convulsions, even though convulsions can happen quickly and suddenly, and in no way are the responses to be used for my personal diving: I just wanted to hear some stories. I know my limits and I dive <1.4pp02 at all times (and keeping a close eye on my total % as well), but there has to be someone out there who has pushed the limits, realized the danger, and backed off safely.

Scott

 

[Kim]

I know there are preliminary signs before convulsions,

This is where you misunderstood my answer. The above statement can be true sometimes - but in other cases it is absolutely not, and there is no warning whatsoever. This is why any answer to your question would basically be meaningless as it couldn't be applied to any other situation at all, but might foster an erroneous impression that it is safe to push the limits as you will get some warning of impending doom. This is a very false idea that could be very dangerous.
The simple facts are you don't want to OxTox and you don't want to have any symptoms either. The area where this happens shifts around with a ppo2 1.6 for a 45 minute exposure using up 100% of your CNS clock (NOAA tables). You don't want to be anywhere near this limit at all. This is why a lower ppo2 like 1.4 is without doubt a lot safer. I believe that the US Navy actually uses ppo2 1.3 as the maximum limit - although I may possibly be mistaken on that.

 

[Daryl Morse]

It seems as though my previous question was misinterpreted -- I know there are preliminary signs before convulsions, even though convulsions can happen quickly and suddenly, and in no way are the responses to be used for my personal diving: I just wanted to hear some stories. I know my limits and I dive <1.4pp02 at all times (and keeping a close eye on my total % as well), but there has to be someone out there who has pushed the limits, realized the danger, and backed off safely.

Scott

This isn't from personal experience, but rather from taking the CSU course.

Symptoms of CNS Toxicity: Convulsions/loss of conciousness, euphoria, nausea, muscle spasms, anxiety, dizziness, irrational behaviour, visual disturbance, ears ringing.

Symptoms of Narcosis: Euphoria, numbness and tingling, dizziness, irrational behaviour, visual disturbance, ears ringing.

Since 5 of the 6 symptoms of narcosis are also symptoms of CNS toxicity, CNS toxicity can potentially creep up with you either not knowing it, or thinking it's narcosis, particularly if one of the symptoms is irrational behaviour. The big difference is convulsions. They are sudden and it's not like you can do anything about them once they happen. Why take the chance?

 

[Uncle Pug]

Why take a chance?

The key is assessing what the risk really is.

 

[Daryl Morse]

I believe that the US Navy actually uses ppo2 1.3 as the maximum limit - although I may possibly be mistaken on that.

I've met some USN divers that have done over 200 fsw on air. USN air tables categorize any dive to 200 fsw or deeper as "exceptional exposure". 200 fsw on air is 1.48 ppo2.

 

[Daryl Morse]

The key is assessing what the risk really is.

How do you definitively assess the risk? There aren't any tables or tests that indicate what the true risk is for a particular person under a particular set of conditions. Even if there were, there are so many variables that alter the level of risk from one dive to the next (e.g., temperature, physical effort, etc.), you can never know for sure.

Even if there was a way to assess the risk to a high degree of certainty, you are still faced with a risk management decision. One person might take a 1 in 10 chance to retrieve an expensive light or a piece of china, another might not. It's a personal decision.