OXTOX limits - MOD, PPO2 or CNS Clock?

[Jax]

I agree that it's undesirable to give students the idea that dipping slightly below their contingency ppO2 in an emergency is going to kill them instantly. But I do think people diving Nitrox should know that toxicity is very unpredictable, and that people have been known to seize at a ppO2 of 2.0 with less than ten minutes of exposure.

And through two classes and six different books, I've never seen any message of "dip below in an emergency" will instantly kill you. However, given drrich2's definition of "lumpers", I can see that kind of person taking away that "breaking your MOD can kill you". Interestingly, I ran into a PADI instructor like that . . . he was so adament, I didn't feel comfortable even discussing it.

In my admittedly uneducated mind, I couldn't perceive how one could on-gas enough O2 to break the PPO2 limit in just a few seconds to a minute. I can imagine, however, this instructor turning out many students with that absolute, mindless fear of breaking the MOD.

 

[Superlyte27]

How do you know that if you have never seen it happen?

Convulsions is pretty hard to mistake?

 

[Superlyte27]

It's not ALWAYS the first symptom, but it sure is the worst. It results in a funeral. Most recreational divers don't use helmets and don't have support crews.

.

So many times that's the fall back argument.... Support Crew.

Lol, do you know why we have COMs in a helmet? Because every friggin day, like clockwork, our idiot tender forgets to put diesel in the compressor, and we run out of gas to breathe. So, we yell, "HEY FRIGGIN MORON, PUT FUEL IN THE COMPRESSOR". Yup, that's about what our support crew amounts to, unless you are talking about a mixed gas dive we're pretty much in the same boat as scuba accept that we can yell at people. Pressure is pressure.

There are literally thousands of people on this board. Who here has actually witnessed a person going into convulsions because of too high PPO2?

 

[PfcAJ]

I don't think the dive buddy of the lady that died at "The Crack" posts on here, nor the Norwegian guy who's buddy switched to the wrong gas and died. Same thing with Richard Mork's buddy. There was a documented case of a diver descending to somewhere in the 70-90ft range on 100% on the Wakulla 2 project in the 90s. He either convulsed or went unconscious, but lived.

And pressure is NOT pressure. Divers wet are way more likely to have symptoms than dry divers.

 

[Superlyte27]

LOL, 90' on 100% are we still talking Apples to Apples? Out of the 1000 views on this post, you posted 3 instances of what you HEARD. The thousands of members on here dive every week, some every day. What have you personally SEEN. If we added up the cumulative dives from every member who has posted on this thread alone, we are literally talking about tens of thousands of dives. Yet, no one here has seen an O2 hit that resulted in convulsions? C'mon, it's not voodoo guys. It's rare. Certainly don't go spend an hour at 2.3ppo2, but this isn't the big scary monster people are trying to sell it to be.

Pressure is pressure. Almost all of us working in the gulf are diving wet. Most of us wear nothing but coveralls, not even a wetsuit (unless it's a mixed gas dive)

 

[berk]

Pressure is pressure. Almost all of us working in the gulf are diving wet. Most of us wear nothing but coveralls, not even a wetsuit (unless it's a mixed gas dive)

I always love a shot of some guy jumping in the water with jeans or Carhart's on.

 

[Superlyte27]

I used to wear Jeans and a long sleeve shirt. Most of the jobs I do are very dirty like Jetting. Then I opted to go with the one peice cover-alls that zip up the front, then I duct tape my steel toed rubber boots and gloves on.

 

[DCBC]

Now, lets go to the commercial field (my field) where we spend lots of time at 1.6ppo2. ...Now, is diving at 1.0, 1.3, 1.4 safer than 1.6? Of course it is. But if 100 people today make a 4 hour dive at 1.6, how many of them are going to take a hit? 99% of the time, zero people in the above scenario will take a hit. For years in the commercial field, I watched this over and over and over. I've NEVER seen an oxygen hit from 1.6ppo2. That doesn't mean that it won't happen to me tomorrow. But the chances are very very slim.

By the way, the absurd idea that convulsions is the first symptom, is just dumb and untrue.

I agree about the 1.6 PPO2, but this applies to commercial divers that have to pass a hyperbaric medical yearly. I too have to remind myself that this isn't a commercial fourum and that divers here dive for recreation. From a training agencies perspective, I understand why the recommended limit is 1.4.

As to convulsions, they say that the first symptoms are disorientation, breathing problems, and tunnel vision, retinal detachment and seizure. Unconsciousness occurs at some point. For me I had no warning whatsoever and just went unconscious.

 

[Jax]

I used to wear Jeans and a long sleeve shirt. Most of the jobs I do are very dirty like Jetting. Then I opted to go with the one peice cover-alls that zip up the front, then I duct tape my steel toed rubber boots and gloves on.

:huh: . . . Will you help me understand that?

 

[Superlyte27]

When you are jetting, basically you are shooting a high pressure 3" water hose underwater to dig a big trench. Sand, sea shells, jelly fish, everything in this jet stream is blown everywhere. So, to keep this crap out of you a little, you tape up every opening in your cover-alls. I wear cheap nylon mesh gloves to protect my hands, but tape them to my sleeves. I wear steel toed rubber boots (like what cement workers wear when working in cement) then tape my coveralls to them so they don't fill with crap.

Oh, and still love the new avatar.