Deaths at Eagles Nest - Homosassa FL

[Storker]

There's one thing that makes me go to the article:

A sheriff's office investigation has found that pair died accidentally after apparently losing track of time and diving to 233 feet while using just air in their tanks.

The depth meant that the duo - who were not certified in cave diving - should have used a trimix combination for their breathing instead of just air, rescue diver Eric Deister told the Tampa Tribune.

He added that they shouldn't have gone deeper than 218 feet due to possible toxic effects.

Could someone more experienced than me in deep air diving explain the practical difference between 218ft (66m) and 233ft (71m) on air? IMO, both of those depths on air basically mean that you're narked out of your skull. Is the difference between 1.596 and 1.701 bar pPO2 really significant?


(if this is a hijack, I apologize)

 

[boulderjohn]

There's one thing that makes me go to the article:



Could someone more experienced than me in deep air diving explain the practical difference between 218ft (66m) and 233ft (71m) on air? IMO, both of those depths on air basically mean that you're narked out of your skull. Is the difference between 1.596 and 1.701 bar pPO2 really significant?

I don't think this is a hijack.

I don't know what happened in the conversation between Deister and the reporter, but in my experience with newspaper reports on diving, you have to assume there must be a brass band playing in the background throughout the interview, thus interfering with the reporter's understanding.

My best guess is that the reporter got some of the information being discussed and included it in the report as evidence of their lack of expertise. There is so much more wrong with what they did that exceeding the threshold for PPO2 is about as insignificant as it can possibly get. Even the 1.6 limit is wrong. Technical divers generally only use 1.6 as the standard for decompression stops only, not for the working part of the dive. The maximum PPO2 during the working part of the dive is anywhere from 1.2-1.4, depending upon which agency belief you are following.

It would take quite some time to list all the mistakes that were part of their dive.

 

[Storker]

My best guess is that the reporter got some of the information being discussed and included it in the report as evidence of their lack of expertise. There is so much more wrong with what they did that exceeding the threshold for PPO2 is about as insignificant as it can possibly get. Even the 1.6 limit is wrong. Technical divers generally only use 1.6 as the standard for decompression stops only, not for the working part of the dive. The maximum PPO2 during the working part of the dive is anywhere from 1.2-1.4, depending upon which agency belief you are following.

Yep, that was basically my conclusion as well: Clueless reporter focuses on an insignificant tidbit of information. However, since I'm basically incompetent WRT deep air (except that I know I'm not going there), I wanted to double-check.

It would take quite some time to list all the mistakes that were part of their dive.

Yup

 

[KellyAsh]

There's one thing that makes me go to the article:



Could someone more experienced than me in deep air diving explain the practical difference between 218ft (66m) and 233ft (71m) on air? IMO, both of those depths on air basically mean that you're narked out of your skull. Is the difference between 1.596 and 1.701 bar pPO2 really significant?

To give my 2 cents on the PP02 question. 1.6 ATA PP02 is called the "contingency limit" to give a buffer for the accepted Maximum PPO2 limit of 1.4 ATA for recreational divers' emergencies, and for tech divers it called a "deco" PPO2, which is used as an acceptable PPO2 level to help with accelerated decompression at shallow depths.

Whether the difference between 1.6 and 1.7 PPO2 will be felt by the diver is a matter of specific circumstances on that day for that diver. We all know that dehydration increases our chances of getting DCS but it is also entirely possible to get DCS for no apparent reason, other than actually getting in the water and diving. It's almost a crap shoot in one respect but we do have a huge impact on our susceptibility to DCS through our or own actions like staying hydrated, keeping in shape, getting enough rest, etc....just staying healthy...or not.

My opinion is that if the diver exercises, is healthy and dives regularly the real world difference between 1.6 and 1.7 PP02 would be negligible if they stayed at that pressure for only a short time (1-2 minutes). After that ongassing and 02 exposure happens faster and faster for each second of time spent at depth.

As you get deeper, things begin to affect you exponentially from atmosphere to atmosphere. In other words, there is a greater impact from 1.7 - 1.8 PP02 than there is from 1.6 - 1.7 PP02. It's the same 1 PP02 change but the deeper depth gives more variance from a healthy state within the human body.

Not too long ago, we had an older diver get bent, while diving the same, very conservative profiles, as a dozen other divers. He was a non-smoker, healthy older guy (but I don't remember specifics on the guy) and got a Type 2 DCS hit that required around 8 treatments to resolve issues.

So, in a nutshell, than answer to your question is "It depends", lol

 

[Tortuga68]

A few different topics getting mixed up here...

• The quote from the article was about Oxygen Toxicity
• Storkers question was about Narcosis
• Kelly has replied talking about DCS

For the purpose of the discussion (about the aticle quote) these 3 topics are not related. As far as PPO2 goes, plenty of divers have experienced 2.31 (100m on Air) or greater and had no problems in completing the dive successfully. Whether that's advisable or not is another matter and depends on the conditions, objective of the dive, personal risk assessment and the availability of viable alternatives (like Trimix). As Kelly's anecdote illustrates, increased PP is not an indicator of DCS.

 

[Storker]

Storkers question was about Narcosis

Actually, it was about both, as both may be an issue at those depths. What I basically wanted to know, was if I was right in assuming that:

1. At both those depths quoted, you'd be more or less equally narked and more or less equally impaired in your task loading and decision making abilities
2. The difference between those two depths is so moderate that O2 toxicity is more or less equally an issue (and not a really pressing issue anyway).

And AFIcan understand from the answers, I was pretty right in those assumptions.

 

[Redshift]

I think this came written like that in the news because they were diving beyond the magical limit for PpO2 of 1.6 bar

 

[Tortuga68]

Storker: I'm inclined to agree that there's not a huge difference in narcosis between 66m and 71m if all other things are equal. In reality though, you could feel okay at 71m one day and off your tree at 66m the next. In other words, the perceived effects of narcosis vary more according to other factors (physical/mental state, task loading, CO2 retention, light/temperature) than pure depth.

Regarding OxTox, you need to consider external factors too but especially exposure (i.e. duration) and physical activity. It's not just about exceeding a 'magic number' and bang you're dead.

The main consideration though should be the potential outcome/consequences: if you OT with a reg in your mouth you're probably going to fit and drown. Narcosis, well a lot of things can happen but it is not going to kill you in and of itself. The dumb decisions (or lack thereof) you make while narc'd may well do, but as a phenomenon it's survivable.

 

[Mouse]

I went to high school with Darrin. As a parent that dives with their child, I can't imagine ever putting my son in a situation like this. Although he is a responsible 15 year old and has the same training I do, I know without a doubt that my attitude and confidence about the dive will have a huge impact on his. He trusts my judgement. If I think he's capable of something he's more willing to take the risk. So I can totally understand why Darrin's son seemed so sure of his ability. Because of my own lack of experience I won't dive with my son alone...I pay a much more experienced diver to come with us.

 

[JDelage]

I'm in the process of reading this thread because I'm fascinated by those stories. Some here have been arguing for a rigid enforcement of a certification system. I am not convinced it would have helped much in this case. I'm convinced Spivey could have gone through the motions - taken the classes, getting certified - and still be a danger to himself and others. The problem here was not a lack of training, it was one of attitude. Sure, it's because of his attitude that Spivey chose not to seek proper training, but if he had been forced to he would have done the training - and probably still gotten himself killed.