OP
Shooter Dan
Registered
Ten Seconds......deep breath.....ten seconds.....deep breath.
OK!
OK!
Tech Nitrox Intro
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And then maybe not... depends on what your instructor knows... and some don't know.
From what you've already mentioned I surmise that you will be learning to use high PO2s to deco after using high PO2s to minimize the risk of DCS on mulitple dives in the 100`150' range.
Just tuck this one away and let it guide you through the maze:
{The principle danger is going to be the Ox tox hit.}
Jarhead
Contributor
Now I'll be the first to admit that I don't know anything about this, but...and feel free to correct me if I'm wrong...but don't you use a deco gas with a high ppO2 (such as 80%) for deco after a dive that you used and bottom gas (Trimix?) with reduced O2 percentage? (I'm not sure I stated that right).
As opposed to using a high O2% deco gas after using high O2% dive (bottom) gas as stated above.
As opposed to using a high O2% deco gas after using high O2% dive (bottom) gas as stated above.
Well I think you guys ran him off
But what I do know is that once you extend the PO2 above 1.4 to 1.6 you run a severe risk of getting an ox tox hit.
From my quick math, if you are diving to 150' the MAX O2% you should have is 28.8%...that works out to a PO2 of 1.6 ATA. For 100', max O2% is 39.6%
Thus, you say you normally dive 32 to 34% O2....and you normall dive to 100ft...that's an avg PO2 of 1.37....now according to my IANTD EANx text...the maximum recreational limits for O2 exposure at that PO2 in 24 hours is 180min....if your doing more than 4 dives...I think you might have exceeded this.
Anyway, this is just what I learned in my basic EANx class through IANTD. I wouldn't exceed these limits...you might want to check into an IANTD class?
As for more of my illustrious theories, if you are going to be using an 80% mix for DECO, I believe DECO stops are done at a high PO2 in order to off-gas, and you would be having to DECO at (approximately) 33 ft. as opposed to (I believe) 20ft. with 100% O2. I think most of the tech divers are now steering away from 80% for that reason, and using 70% for a deeper stop, then switching to 100% O2 for their final stop....I'm sure someone will correct me if I'm wrong.
Anyway, I too am going to be looking in the direction of deeper dive before too long...it seems to be interesting to me, but I am going to be sure I get some good education and knowledge before I jump in feet first.
From my quick math, if you are diving to 150' the MAX O2% you should have is 28.8%...that works out to a PO2 of 1.6 ATA. For 100', max O2% is 39.6%
Thus, you say you normally dive 32 to 34% O2....and you normall dive to 100ft...that's an avg PO2 of 1.37....now according to my IANTD EANx text...the maximum recreational limits for O2 exposure at that PO2 in 24 hours is 180min....if your doing more than 4 dives...I think you might have exceeded this.
Anyway, this is just what I learned in my basic EANx class through IANTD. I wouldn't exceed these limits...you might want to check into an IANTD class?
As for more of my illustrious theories, if you are going to be using an 80% mix for DECO, I believe DECO stops are done at a high PO2 in order to off-gas, and you would be having to DECO at (approximately) 33 ft. as opposed to (I believe) 20ft. with 100% O2. I think most of the tech divers are now steering away from 80% for that reason, and using 70% for a deeper stop, then switching to 100% O2 for their final stop....I'm sure someone will correct me if I'm wrong.
Anyway, I too am going to be looking in the direction of deeper dive before too long...it seems to be interesting to me, but I am going to be sure I get some good education and knowledge before I jump in feet first.
OP
Shooter Dan
Registered
AquaTec, is that all you can contribute?
I would expect more from a seasoned veteran, Yeh?
You are an instructor, right? I'll never do you type of diving and you probably won't be spearfishing and time soon.
My technical question was a reasonable one. Maybe too elementary for your level, but isn't that what these boards are for.
If you had questions regarding spearing a 70lb amberjack, I would try to add information that was worthwhile.
Although you didn't better this thread with your comment, you could if you wanted to.
If not that's fine, Sit back and enjoy the thread.
I would expect more from a seasoned veteran, Yeh?
You are an instructor, right? I'll never do you type of diving and you probably won't be spearfishing and time soon.
My technical question was a reasonable one. Maybe too elementary for your level, but isn't that what these boards are for.
If you had questions regarding spearing a 70lb amberjack, I would try to add information that was worthwhile.
Although you didn't better this thread with your comment, you could if you wanted to.
If not that's fine, Sit back and enjoy the thread.
The purpose of decompression gas(es) is to eliminate the inert gas dissolved in your tissues. This can be done by using a high FO2 gas at the appropriate depth. This would result in a PPO2 of 1.6 for a resting deco.
A deco gas of 80% oxygen is a poor choice for decompression because the balance is an inert gas that will reduce the effectiveness of the inert gas elimination by reducing the partial pressure gradient of both gases.
As Pug pointed out the primary concern would be an oxtox hit. It is critical that you have the right training to address this and have a buddy with you that has the skills to save your ass (and vice versa). Also you do not want to dive to high PPO2s over and over. You need to reduce the working PPO2, and plan the decompressions such that you are not accumulating an excess exposure. To do this use helium. The advantages of using helium for the depth and number of exposures you are talking about are innumerable and are the only sensible approach. A tech nitrox course is insufficient.
For extended profiles 50% is used at 70 FSW (and up) and 100%
at 20FSW
omar
A deco gas of 80% oxygen is a poor choice for decompression because the balance is an inert gas that will reduce the effectiveness of the inert gas elimination by reducing the partial pressure gradient of both gases.
As Pug pointed out the primary concern would be an oxtox hit. It is critical that you have the right training to address this and have a buddy with you that has the skills to save your ass (and vice versa). Also you do not want to dive to high PPO2s over and over. You need to reduce the working PPO2, and plan the decompressions such that you are not accumulating an excess exposure. To do this use helium. The advantages of using helium for the depth and number of exposures you are talking about are innumerable and are the only sensible approach. A tech nitrox course is insufficient.
For extended profiles 50% is used at 70 FSW (and up) and 100%
at 20FSW
omar
...that chip on your shoulder is a huge snag hazard... you missed what AquaTec was saying by a mile! (as well as what the rest of us are saying of course.)
He was chastising us for running you off.... in that he was mistaken.... your not gone.... but be that as it may.... AquaTec was actually sticking up for you!
You just spit into the wind dude.
well i will thow in a couple of thoughts
Nothing wrong with 6 or 7 dives a day as long as you manage depth, time, and SI. Also I know that when I used to hunt it was always solo so if you are doing the same then buddy dependency is not an opption. just make sure you have some redundency
a tox hit probability can be reduced by reducing the Po2, but by doing so you will increase nitrogen loading which will increase fatiege and risk of dcs. you can walk this tight rope with good planning and management
I recomend using a nitrox computer that will track your CNS and dive profile for this type of diving. As for training, caring deco bottles etc, may not be conducive to the type of diving you are doing...hunting. I think that by watching your cns and managing other aspects of your diving, and getting a good nitrox computer to track cns etc you can do those dives
I know this because I used to do six dives a day at work as a dive guide at molokini island and then go do a couple of hunting/fun dives at night, using air...but that was a different
time. in those days my room mates and I only ate what we could get from the ocean and then suplement it with beer. sort of the hawaiian scuba instructors kraft dinner
Nothing wrong with 6 or 7 dives a day as long as you manage depth, time, and SI. Also I know that when I used to hunt it was always solo so if you are doing the same then buddy dependency is not an opption. just make sure you have some redundency
a tox hit probability can be reduced by reducing the Po2, but by doing so you will increase nitrogen loading which will increase fatiege and risk of dcs. you can walk this tight rope with good planning and management
I recomend using a nitrox computer that will track your CNS and dive profile for this type of diving. As for training, caring deco bottles etc, may not be conducive to the type of diving you are doing...hunting. I think that by watching your cns and managing other aspects of your diving, and getting a good nitrox computer to track cns etc you can do those dives
I know this because I used to do six dives a day at work as a dive guide at molokini island and then go do a couple of hunting/fun dives at night, using air...but that was a different
time. in those days my room mates and I only ate what we could get from the ocean and then suplement it with beer. sort of the hawaiian scuba instructors kraft dinner
OP
Shooter Dan
Registered
What a great lunch. Did I write all of that stuff? Gezz that must have been hungry, evil Shooter Dan.
I respect your position and appreciate the information passed on. I'll be researching other posts on this topic and articles in prep for my class. As you can tell, words in print can be misconstrued or taken out of context.
Guys, I really didn't want to flounder and stir up the viz on my first dive here.
If you have any related articles or must know stuff, shoot it to me if you have some time.
Thanks
Standing by
I respect your position and appreciate the information passed on. I'll be researching other posts on this topic and articles in prep for my class. As you can tell, words in print can be misconstrued or taken out of context.
Guys, I really didn't want to flounder and stir up the viz on my first dive here.
If you have any related articles or must know stuff, shoot it to me if you have some time.
Thanks
Standing by
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