A Game: WHAT WOULD YOU DO?

[billsreef]

Tim,

One of the things they teach in Rescue, and it seems the same as you've learned as a wilderness guide, is considering the risk to yourself. You need to analyze the situation, determine your risk factor and decide if that risk factor is acceptable. That risk factor is going to be dependent on your level of training and what gas mix your diving. In some cases you'll come up with the answer that there is more likelihood that trying to rescue someone will result in both of you needing rescue. In that case, your best option, and the victims best option, is for you to head to the surface post haste and get qualified help. If it's a popular dive spot, you'll most likely find some divers present that are both qualified and equipped to effect the rescue. The most important thing is not turning the scenario into two divers needing rescue, as you'll not only failed at saving the victim, but quite possibly delayed his chances at getting help while putting yourself in the position of needing rescue.

While I have been Rescue trained, there are going to be instances where I wouldn't rescue the victim myself. If I have insufficient air or diving a nitrox blend that wouldn't allow me to go to the required depth I would head for the surface and either get someone else to go for the victim, or grab a fresh tank of air to go back while getting someone to call for EMS. In any and all events, remember to not make yourself a victim

 

[tgreene]

If I'm already down 60' and as an OW only diver I have 2 things to consider...

1) It will take me 2 minutes to safely hit the surface and yell for additional help.

2) I'm an OW diver which means that I'm on Air, and since I just began the dive I'll likely have at least 2400psi depending upon who filled my tanks. Some will give me 3000, while other s will only blow them to 2600... Again, let's assume I have 2400.

-Tim

 

[SeaJayInSC]

Well, I'm impressed. You know, HONESTLY, Tim, most new divers don't THINK like you are. It's super-cool that you're chewing on this and coming up with questions... Good ones, at that.

OxTox isn't a situation that happens instantly... For a diver to 'Tox at 130' on EAN36 (MOD100), he'd have had to have been there a while... Like several minutes.

A better example would be a diver on 50% oxygen (EAN50, or MOD70) 'Toxing at 130'. I would think that by the time the diver was passing 90' or 100', he'd pretty much be fully into his 'Tox. Unfortunately, that would have been a bad example, as MOD70 isn't something that you'd normally find sitting around most dive sites unless someone was doing some serious decompression.

...So while it's true that a diver on MOD100 would 'Tox at 130', it would take several minutes for it to happen in most people.

...But since you're mulling things over, keep in mind that your gas - air - is MOD190... So in terms of OxTox, you're safe on it at 130'... Although probably narked more than you know. It's not the ideal gas to be breathing there, but it works without risk of 'Toxing.

...So are we recommending that you dive below depths that you were trained for? No... Of course not. But Billsreef and I both have been trained for 130', so our answers are "What we would do."

For you, you're stuck between having to choose to stay within your training OR save the dude... One or the other. Which you choose would be your call.

...But with all of this in mind, you can solve the issue NOW by taking your Advanced and then Rescue courses. There. Ya made me say it.

 

[SeaJayInSC]

Great discussion, by the way.

 

[tgreene]

<a href=showthread.php?s=&postid=15069829#post15069829 target=_blank>Originally posted</a> by SeaJayInSC
Well, I'm impressed. You know, HONESTLY, Tim, most new divers don't THINK like you are. It's super-cool that you're chewing on this and coming up with questions... Good ones, at that.

OxTox isn't a situation that happens instantly... For a diver to 'Tox at 130' on EAN36 (MOD100), he'd have had to have been there a while... Like several minutes.

As a diver that just happened across him, I would have absolutely no way of knowing how long he had been there, which completely negates the issue as too how long he has been there or can continue to stay at that depth while a "qualified" rescuer is sought!

So I'm good to just under 190' huh..? Hmmmmmmmmmmmm! :smokin:

-Tim

 

[billsreef]

<a href=showthread.php?s=&postid=15069905#post15069905 target=_blank>Originally posted</a> by tgreene
So I'm good to just under 190' huh..? Hmmmmmmmmmmmm! :smokin:

-Tim

As far as oxtox goes Narcosis is another story, as is decompression which will be necessary. Depending on your tolerance for narcosis, you might be fine or narcing out and heading even deeper or some other stupid thing. In any event, your definitely in the realm of mandatory decompression at that depth.

 

[tgreene]

Obviously.

 

[tgreene]

<a href=showthread.php?s=&postid=15069829#post15069829 target=_blank>Originally posted</a> by SeaJayInSC
Well, I'm impressed. You know, HONESTLY, Tim, most new divers don't THINK like you are.

Thank you.

 

[SeaJayInSC]

Hey... Let's run with this one. Tim, I know you've not been trained yet to handle this question, but I want to shine a little light on some of the stuff you'll learn in the future... 'Cause I think you're the kind of mind that would really get excited about this stuff.

There's a place in North Florida called "Forty Fathom Grotto." I have dived there many times. It's beautiful.

In case you don't know, a fathom is about six feet. True to it's name, this place is 240' deep, and is owned by Hal Watts, a virtual diving legend.

There, Hal teaches a course called "Deep Air," where he takes students to the bottom of the grotto on air.

What two major issues are wrong with this scenario?

 

[tgreene]

Obviously narcosis and toxicity, but I would also question what the point in even TEACHING something that goes beyond the realm of minimal safety margins.... ie: He's taking students 50' below the maximum 190' level you posted above.

If something goes bad, a diver cannot possibly be "rushed" to the surface, because of all of the stages of mandatory decompression that would be required before surfacing.

Can he even get insurance..?

On the otherhand if they dove on surface Hookah systems, then this would all be a moot point!

-Tim

 

[SeaJayInSC]

That's funny... Narcosis and Toxicity... Those are the two.

What's funny is that you've got a great point that there's also the issue with the overall philosophy, the elevated decompression obligation over other gasses, and the probable legal issue with insurance.

I don't know if he's got insurance or not. I've never been one of his students.

...Just goes to show, just 'cause there's training offered, doesn't mean that it's GOOD training.

...And just 'cause someone's famous, doesn't mean that they're someone that should be followed.

 

[SeaJayInSC]

Let's do an exercise.

Again, this is directed to you, Tim... Again, this is a bit out of your training thus far, but I want to show you what's in the future for your training.

You're diving on 190 mix to 100 feet. It takes you exactly one minute to get down to the bottom. You stay there 8 minutes, and begin an ascent. You ascend at 30' per minute to 40 feet and stop and spend one minute there. Then you ascend to 30 feet and spend two minutes there. You ascend to 20 feet and spend four minutes there, and then ascend to 10 feet and spend eight minutes there.

When you surface, how much gas is in your tank? What psi does your guage read?

 

[tgreene]

I do pay attention as well as read everything that I can get my hands on, then thoroughly weigh the balance of specific issues using a set of hypotheticals... It's not algebra, so when data is missing I typically resort to a "worst case scenario" set of facts and figures to formulate the best possible solution.

So do I get a pass yet for all of the *** chewing that I received last week for my n00b solo..?

-Tim

 

[SeaJayInSC]

LOL!

How 'bout an apology instead?

Sorry I chewed your ***. I don't want to even consider the concept of having one of my friends hurt.

...And I'd rather have the situation where I'm apologizing than burying...

 

[SeaJayInSC]

<a href=showthread.php?s=&postid=15070374#post15070374 target=_blank>Originally posted</a> by tgreene

On the otherhand if they dove on surface Hookah systems, then this would all be a moot point!

-Tim

Why?

 

[tgreene]

<a href=showthread.php?s=&postid=15070473#post15070473 target=_blank>Originally posted</a> by SeaJayInSC
Let's do an exercise.

Again, this is directed to you, Tim... Again, this is a bit out of your training thus far, but I want to show you what's in the future for your training.

You're diving on 190 mix to 100 feet. It takes you exactly one minute to get down to the bottom. You stay there 8 minutes, and begin an ascent. You ascend at 30' per minute to 40 feet and stop and spend one minute there. Then you ascend to 30 feet and spend two minutes there. You ascend to 20 feet and spend four minutes there, and then ascend to 10 feet and spend eight minutes there.

When you surface, how much gas is in your tank? What psi does your guage read?

Based upon the RDP, you can only have a maximum of 20 minutes bottom time at 100' and the total time calculations indicate a bottom time of just a hair over 27minutes, but it's all cool since the 8 minute NDL is being met at the 10' depth, which was preceeded by the 4 minute 20' stop.

The curve ball for me was in calculating the ascent rate based upon 30' per minute being used throughout the dive and adding that to the TBT.

Clearly however, it's impossible for me to give you a PSI reading because that's going to depend upon 3 primary factors, with the only plausible answer falling solely upon #3.

1) What size tank was used..?

2) What was the beginning tank pressure..?

3) What is the SAC rate of the diver..?

If I'm the diver using an AL80 that was blown to the 2600psi that my LDS fills to, it's gonna be really dicey by the time I surface so I'll likely be on fumes... If I'm running low, I'll slow my breathing by taking super slow deep breaths from my diaphragm rather than "normal breathing", and when I see that I'm running lower and lower on air, I'm gonna skip breathe as long as I can while I'm stationary.

If you're the diver on that same 2600psi AL80 , then the scenario will be entirely different due to you likely having a SAC rate of close to 50% of mine, so you'll happily surface with 500psi.

Do I win a cookie..?

-Tim

 

[tgreene]

<a href=showthread.php?s=&postid=15070529#post15070529 target=_blank>Originally posted</a> by SeaJayInSC
LOL!

How 'bout an apology instead?

Sorry I chewed your ***. I don't want to even consider the concept of having one of my friends hurt.

...And I'd rather have the situation where I'm apologizing than burying...

Maybe I should explain the art of sarcasm to you someday... Over apres-dive beers of course!

-Tim

 

[tgreene]

<a href=showthread.php?s=&postid=15070562#post15070562 target=_blank>Originally posted</a> by SeaJayInSC
Why?

As I understand it, aside from the obvious unlimited amount of air available, the non-compressed pumped air does not suffer from the same expansion/contraction issues as compressed air at depth. Loading, narcosis and toxcicity YES, but the unlimited air supply will alleviate the need for various stage gasses and their own relative off-gassing stops.

-Tim

 

[SeaJayInSC]

Nah, I owed you the apology anyway.

Well, I'm impressed... Seriously. That question is typically one addressed only in "technical" classes - years ahead of where you are at the moment in your training.

Yet, you really seem to have a grasp on this stuff.

The question isn't a fair one... You're right on as to why... 'Cause I haven't given you a SAC rate. I was wondering if you were aware of such a thing, and here you come out with not only the concept, but the correct terminology for the concept.

Let's go ahead and give you a SAC rate... I can't imagine that you've bothered to try to figure your real one out yet - it's going to change considerably over your 50 first open water dives anyway.

Let's also do some rounding to make things simpler, calculations-wise.

Let's say that you've got a tank with 3000 psi in it, let's say that that's 80 cuft of gas (an AL80 is actually 77.7 cuft of gas at 3000 psi, but let's round), and let's say that you have a SAC ("surface air consumption" for those of you who don't know) rate of 1.0... That's a consumption of 1 cuft of gas at sea level per minute.

Let's also say that the SAC rate stays consistent - that is, you don't find yourself exerting undue strain during your dive (causing your SAC rate to rise or change).

Then:

1 minute at an average depth of 50ft (which equals about 2.5 atmospheres): 2.5 cuft of gas used.

8 minutes at 100 feet, which is basically 4 atmospheres: 32 cuft of gas used.

1 minute at an average of 85 feet, which is basically 3.5 atmospheres: 3.5 cuft of gas used.

1 minute at an average of 55 feet, which is basically 3 atmospheres: 3 cuft of gas used.

1 minute at 40 feet, which is just over 2 atmospheres: round to 3 cuft of gas used.

2 minutes at 2 atmospheres: 4 cuft of gas used.

4 minutes at around 1.5 atmospheres: 6 cuft of gas used.

8 minutes at less than 1.5 atmospheres: about 12 cuft of gas used.

Total gas used: 66 cuft.

If 80 cuft = 3000 psi, then what's left - 14 cuft = 525 psi.

I did that using this math: 3000/80 = x/14.

There's that algebra you asked for.

Of course, you'll notice that I didn't plan for any gas usage during each of the 10' ascents, but that exercise will give you an idea.

It'll also show you that if you have a SAC rate of 2.0, you'll know that there's no way in heck that you've got enough gas to do an 8-minute dive to 120 feet.

The reality is, you probably don't have enough gas to do this even at a SAC rate of 1.0 because you wouldn't have enough gas to do this profile if your buddy suddenly had an issue with his rig and needed you to do an out-of-air right at the 8-minute mark at 120 feet. There's no way you'd have enough gas to complete those stops WHILE DONATING.

...But I'm not trying to help you plan a dive... Just to get you to start thinking about this kind of stuff, which is the basis for gas management, which becomes increasingly more complex as you go deeper, stay longer, increase the number of gasses that you're using, etc.

One thing that I saw that you brought up - one of the places I saw your mind go to when you began thinking about this dive... Was the difference between what I am calculating as "bottom time" and what your dive tables say.

For example, I talked about an eight minute bottom time. You talked about a total dive time. Did you notice that? There's a big difference between the two. I'd like to explore that area some more with you to really get your brain cells warmed up.

 

[SeaJayInSC]

<a href=showthread.php?s=&postid=15070809#post15070809 target=_blank>Originally posted</a> by tgreene
As I understand it, aside from the obvious unlimited amount of air available, the non-compressed pumped air does not suffer from the same expansion/contraction issues as compressed air at depth. Loading, narcosis and toxcicity YES, but the unlimited air supply will alleviate the need for various stage gasses and their own relative off-gassing stops.

-Tim

Negative!

The profiles for a hookah diver at a given depth as compared to a diver on a tank of air at the same depth should be identical. The expansion/contraction of the breathing gas has nothing to do with it... It's all about the diver's body - and the ambient pressure. Whether the air comes from a tank or an umbilical doesn't matter.

The reason why you've probably been told that "hookah divers don't worry about their decompression obligation" is because they have an unlimited supply of air. They simply stay down until their decompression is finished. A scuba diver, on the other hand, better have planned to have enough breathing gas to be able to complete his deco - else he'll have to eventually make the choice between getting DCS (or "the bends") or drowning.

...Which is why, as a diver's dives get increasingly deeper, longer, and more complex, "gas management" - that is, making sure that you have enough gas to complete all obligations - becomes increasingly more important.