What happened to Cozumel?

[StreetDoctor]

Can you explain to us how he could be in danger breathing nitrox from a membrane as air while staying above 96 feet?

Oxygen toxicity can happen from repetitive EAN dives just as easily as it can happen from violating partial pressure limits (depth).

Pardon my hostile response but it’s not really my position to educate anyone here on this. Especially after being ridiculed in this thread.

Here’s some light reading but Google is your friend. Your dive computer should give you a CNS % GGUN says he dives “multiple” morning tanks and sometimes an evening tank all while not knowing what he’s breathing. It would be very easy to get oxygen toxicity in this case regardless of whether his computer thinks he’s breathing air or nitrox.

The Science Behind Oxygen Toxicity and Its Impact on Divers

Learn about the science behind oxygen toxicity and how it can impact divers. Discover the symptoms, causes, and prevention methods to ensure a safe diving experience.

darwynhealth.com

 

[StreetDoctor]

I speak of safety and risk, and you speak of rules; it's not the same thing. PADI rules say (or used to, anyway) that an OW certed diver cannot dive deeper than 60 feet. If there were jail sentences handed out for violating a certifying agency's rules most of us would have served time.

A large majority of rules exist in the name of safety… When you get on a dive boat I’m sure the waiver you’re signing also says you agree to dive in the parameters of your certification so you’re also being untruthful with the boat operator.

 

[ChrisM]

Oxygen toxicity can happen from repetitive EAN dives just as easily as it can happen from violating partial pressure limits (depth).

Pardon my hostile response but it’s not really my position to educate anyone here on this. Especially after being ridiculed in this thread.

Here’s some light reading but Google is your friend. Your dive computer should give you a CNS % GGUN says he dives “multiple” morning tanks and sometimes an evening tank all while not knowing what he’s breathing. It would be very easy to get oxygen toxicity in this case.

The Science Behind Oxygen Toxicity and Its Impact on Divers

Learn about the science behind oxygen toxicity and how it can impact divers. Discover the symptoms, causes, and prevention methods to ensure a safe diving experience.

darwynhealth.com

Again though, happy to be educated otherwise but excess O2 from a membrane system would be virtually impossible wouldn’t it? Not really seeing how the N percentage could be *lower than ambient

And the PP02 issue is pronounced with EANx because people use it to dive deeper and longer. GGunn doesn’t. I’ve done a lot of liveaboards with 4-5 dives a day and never come close to breaking 1.4. I dont think 2 conservative morning dives plus an occasional afternoon dive is going to push that

For the record, I think best practice is to analyse

 

[StreetDoctor]

Maybe if you’re only doing one dive a day. Either way it’s a terrible habit to not know what you’re actually breathing.

 

[StreetDoctor]

Again though, happy to be educated otherwise but excess O2 from a membrane system would be virtually impossible wouldn’t it? Not really seeing how the N percentage could be *lower than ambient

And the PP02 issue is pronounced with EANx because people use it to dive deeper and longer. GGunn doesn’t. I’ve done a lot of liveaboards with 4-5 dives a day and never come close to breaking 1.4. I dont think 2 conservative morning dives plus an occasional afternoon dive is going to push that

For the record, I think best practice is to analyse

More reading-

Shearwater and the CNS Oxygen Clock

The question of what CNS oxygen exposure is safe can spark heated debate among technical divers. This reflects the seriousness of CNS oxygen toxicity when diving. This article sidesteps that debate, and focuses solely on how Shearwater dive computers calculate the CNS value.

shearwater.com

The equation is about accumulative exposure, duration, and partial pressure levels. I’ve been able to push the CNS clock doing recreational dives in Bonaire just by doing 4-5 dives a day multiple days in a row.

 

[ggunn]

...it’s not really my position to educate anyone here on this.

You got that right.

... It would be very easy to get oxygen toxicity in this case regardless of whether his computer thinks he’s breathing air or nitrox.

Again, I disagree. I dive conservatively these days; one morning dive to 80' and another to 60' on nitrox is not going to get me anywhere near O2 toxicity irrespective of whether I do a night dive or not. I analyzed tanks when I first started diving nitrox and set my computer up for it, so I know this from the data I got.

 

[ChrisM]

Maybe if you’re only doing one dive a day. Either way it’s a terrible habit to not know what you’re actually breathing.

On this I agree with you. It doesn't necessarily make it unsafe *depending on the circumstance*

If I were doing a front yard dive at Blue Angel, where I need a shovel to get below 20 feet, I would not care what the mix is. I mean, i grab what is advertised as an air tank, but without testing, who knows? That applies on all boats as well, we all assume that an air tank is 21/79. May not be, but I haven't met anyone in 30 years of diving that tests an air tank.

Again, normalization of deviance is a thing, and a danger to be avoided especially in diving. If someone were regularly diving EANx at EANx limits and never testing, that's a problem. We did a Red Sea liveaboard a couple years ago, they had a European clientele so mostly DIN tanks with adapters. They got a faulty o ring shipment, we had first stages blowing every dive. Yet we all kept diving, knowing this risk, which was STUPID and I kick myself for it. I think we had 10 such failures, including one at 70 fsw. (my eventual failure only occurred at about 40 feet deep on a descent). We all were very experienced, diving with buddies, and somehow that just became an accepted risk, which should NEVER have been accepted. It was very weird to observe both in others and in myself, what we were willing to accept as an acceptable risk.

I don't feel like scrolling back to the top, but I think you continued to dive without analyzing? Same thing.

 

[ChrisM]

More reading-

Shearwater and the CNS Oxygen Clock

The question of what CNS oxygen exposure is safe can spark heated debate among technical divers. This reflects the seriousness of CNS oxygen toxicity when diving. This article sidesteps that debate, and focuses solely on how Shearwater dive computers calculate the CNS value.

shearwater.com

The equation is about accumulative exposure, duration, and partial pressure levels. I’ve been able to push the CNS clock doing recreational dives in Bonaire just by doing 4-5 dives a day multiple days in a row.

Yeah, I'm aware of how PP02 is measured. But he's doing at most, 3, and usually 2.

 

[BRT]

Oxygen toxicity can happen from repetitive EAN dives just as easily as it can happen from violating partial pressure limits (depth).

Pardon my hostile response but it’s not really my position to educate anyone here on this. Especially after being ridiculed in this thread.

Here’s some light reading but Google is your friend. Your dive computer should give you a CNS % GGUN says he dives “multiple” morning tanks and sometimes an evening tank all while not knowing what he’s breathing. It would be very easy to get oxygen toxicity in this case regardless of whether his computer thinks he’s breathing air or nitrox.

The Science Behind Oxygen Toxicity and Its Impact on Divers

Learn about the science behind oxygen toxicity and how it can impact divers. Discover the symptoms, causes, and prevention methods to ensure a safe diving experience.

darwynhealth.com

Please map out 5 Cozumel dives over a day under 96 feet and tell me how you could exceed the allowable limits. I might mention that deco divers routinely exceed these limits with impunity.

Edit: Years ago I studied this when I started mixing my own nitrox. After careful study I understood that the way I dive there was no possible way to exceed these limits. We spend too little time at max depths. If we were to take our AL80's to 96 feet with 36% and spend the whole dive there our bottom times would be reduced so low that we could never reach the 180 minutes in a day.

 

[StreetDoctor]

But he's doing at most, 3, and usually 2.

He just said "multiple" tanks in the morning in addition to an evening dive. There are enough scenarios I could think of where that lackadaisical attitude could bite you in a permanent way where I would never want to dive with a person with this mindset, or witness their death by just being on the same boat.

If I had that mindset and practice for 10 years of diving and then do a liveaboard and do 4-5 dives a day every day for a week spaced in a way to never really get back to "0" while not having analyzed a tank or understood the CNS clock (for the last decade) because "rules dont matter".... See where I'm coming from? Maybe it's overly cautious but it's easy enough to analyze a tank it's stupid not to.