tribaltim
Contributor
Why is it exactlly that recreational diving should not be done past 130' enen on Nitrox or is it alright to go deeper on nitrox as long as your well educated in that area?
Going past 130'
- Thread starter tribaltim
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Spoon
Contributor
tribaltim:
the deeper you go on air the more you are prone to nitrogen narcosis, the deeper you go on nitrox the more you are prone to oxygen toxicity. bitrogen narcosis in itself is not fatal but bec you are in an impaired state you could fail to react to impending problems which may arise at depth. on the other hand, oxygen toxicity is dangerous because you can pass out and drown.
their is a reason not going beyond 130'. its a balance you have to juggle. if you want to go beyond that then you better be breathing some form of mixed gas that will allow you to go beyond this depth safer and even have longer bottom times.
Added to the above your NDL at depths greater than this is so short that you will incur a deco obligation very quickly and therefore not be able to immediately ascend to the surface. If you want to go deeper than this then you should have more training than a normal 'recreational' diver has.
OP
tribaltim
Contributor
Kim:
I appreciate the knowledge looks like I better get cracking on the advanced training then because I can see right now that their is no way I'm going to be satisfied with staying at 130'. Hope to keep in touch with you both thanks again for the comments...
I see that you are in Okinawa. Most of the good dive sites there are within the recreational depths. I would really suggest it's not a bad plan to get a fair amount of practice in before you go further. As the saying goes:
"There's nothing worth dying for down there."
By the way.......welcome to ScubaBoard!
"There's nothing worth dying for down there."
By the way.......welcome to ScubaBoard!
OP
tribaltim
Contributor
Kim:
Yea, I believe your right! I have already read a lot of good threads and I don't think I'm going past 130' until I knock out a few more dive classifications besides it's really cheap to get certified over here and I have a couple more years on the island. I can't wait to check out my new dive computer and gear. Darn Typhoon hopefully next weekend I'll be in the water.......Thanks again brother.......
A lot of the recreational diving rules have come from navy diving.
The 130-ft limit came from the fact that the navy divers that used hart hat`s and was hoisted up by a platform. To send a diver down to 130 ft and bring him up before a no deco limit was reached was a waist of time, if he went deeper, as he could hardly do any work for the bottom time he had. This 130-ft was set as a no deco limit, not a max depth. Note that the recreational dive tables no deco limit is less than the navy tables used to be and still are. The max ascent rate at first was also set by the navy wanting to bring divers up as fast as possible to get the gear, and just pop the diver in the hyperbaric chamber for decompression. But it was a flip by the people that want to bring divers up, that wanted 100-ft/ min and the hoisters that wanted 25 ft/min. At the end 60 ft/min was agreed on. Recreation diving later brought this down.
But the real issue is that, the deeper you go, the bigger the risk gets, as you are further from the surface when something goes wrong. But note, nitrogen narcosis is not the limiter in air dives, its the oxygen toxicity. Oxygen above 1.4 ATA PO2 is starting to push it, esp. on a cold strenuous dive. Above 1.6 ATA PO2 you really risk getting convulsions from oxygen toxicity. You might tuff out narcosis, but to tuff out convulsions is a different story. 66 meters is 1.6 ATA PO2 (Rounded) on an a air dive.
My advice is, if you want to do deep dives. First think why you want to. Then think about if the risk is worth it. And only if you accept the risk. Go get the right training for the diving you want to do.
Happy diving.
The 130-ft limit came from the fact that the navy divers that used hart hat`s and was hoisted up by a platform. To send a diver down to 130 ft and bring him up before a no deco limit was reached was a waist of time, if he went deeper, as he could hardly do any work for the bottom time he had. This 130-ft was set as a no deco limit, not a max depth. Note that the recreational dive tables no deco limit is less than the navy tables used to be and still are. The max ascent rate at first was also set by the navy wanting to bring divers up as fast as possible to get the gear, and just pop the diver in the hyperbaric chamber for decompression. But it was a flip by the people that want to bring divers up, that wanted 100-ft/ min and the hoisters that wanted 25 ft/min. At the end 60 ft/min was agreed on. Recreation diving later brought this down.
But the real issue is that, the deeper you go, the bigger the risk gets, as you are further from the surface when something goes wrong. But note, nitrogen narcosis is not the limiter in air dives, its the oxygen toxicity. Oxygen above 1.4 ATA PO2 is starting to push it, esp. on a cold strenuous dive. Above 1.6 ATA PO2 you really risk getting convulsions from oxygen toxicity. You might tuff out narcosis, but to tuff out convulsions is a different story. 66 meters is 1.6 ATA PO2 (Rounded) on an a air dive.
My advice is, if you want to do deep dives. First think why you want to. Then think about if the risk is worth it. And only if you accept the risk. Go get the right training for the diving you want to do.
Happy diving.
Spoon
Contributor
Kim:
ive heard this line a lot of times in the last couple of days
This confused me to no end when I first started so, just in case someone else gets just as confused...WICKED_WIZARD:
Oxygen gets toxic at a certain amount. We don't have to worry about it at sea level, even breathing 100% oxygen but higher densities aren't safe. When you go under, the air you're breathing is compressed and if you're breathing air, you're breathing 21% oxygen at the surface.
At 33ft (2 atmosphere), the air you're breathing has doubled in pressure so you're now breathing the equivalent if 42% oxygen. 3 atmospheres, 63%, etc.
All this is basic OW stuff but it correlates to the 1.6 ATA stuff people throw around. 160% oxygen is toxic, as 140% is the same as 1.4. When figuring it out, always be sure to account for the 1 atmosphere at the surface!
This applies even more when using nitrox since by using it, you're increasing the amount of oxygen you're breathing. If you're using Nitrox at 34%, you need to know at what depth it becomes toxic. 34% is toxic at about 120 feet, a depth ordinarily safely within the recreational limits. Sure you could push it, some people have successfully returned from very deep dives on air but that doesn't mean it's safe to do so, especially without extensive training and fully understanding the risks. Nitrox will help you stay down longer and you'll feel better for using it but it's not a gas for deeper diving.
Guys...please consider that we are in the New Divers & Those Considering Diving forum. PPOs etc is learnt in the Nitrox course - not OW AFAIK. The Internet isn't really the place to learn it!!! All divers should dive within their training and if they want to do more they should get more real training.
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