No Limit verses Remaining Bottom Time (RBT)

[KevinNM]

No, CNS Oxy tox is random largely. Tests showed that some people could last for an hour at high PO2s, the same people would then go into convulsions after a few minutes the next day. Sometimes the first symptom is a convulsion, other times they had the full spectrum of symptoms first. In addition, susceptibility to CNS hits is greatly increased by being immersed in water for reasons that are not well understood and having a convulsion in a chamber is usually just unpleasant, vs having one in the water - which is highly fatal. So you can usually handle a much higher PO2 in a dry chamber than you can safely handle in water and if you have a convulsion in the chamber the attendant just pulls the mask off and you breath the air in the chamber and recover.

Doing dangerous things for no real reason other then it's convenient is normalization of deviance. So yeah, the chance of something bad happening per minute you have a high PO2 is pretty small, but the impact can be very high. To go back to the classic study of this: Pieces of foam had been falling off the space shuttle tanks bipod ramp for years, hence it was safe to allow it to continue, right? What could a little piece of foam do to the shuttle?

 

[Hatul]

As was already mentioned by others the RBT has to do with the gas supply and tells you how much time you have before you have to ascend at the recommended rate with all the safety/deco stops and still have reserve pressure at surface, assuming your ventilation stays the same. It's one of the nice features of the Galileo.

It has nothing to do with non deco time or oxygen toxicity.

 

[hroark2112]

Also realize that the PPO2 setting on your computer is just for the actual alarm, not for any kind of calculations. Unless you brought a shovel and are digging your way deeper, you'll be nowhere near 1.4 PPO2.

Knowing your computer and what it is telling you is important. Like....really important. Learn it before getting back in the water please!!

 

[jboneng]

Also realize that the PPO2 setting on your computer is just for the actual alarm, not for any kind of calculations. Unless you brought a shovel and are digging your way deeper, you'll be nowhere near 1.4 PPO2.

Knowing your computer and what it is telling you is important. Like....really important. Learn it before getting back in the water please!!

Maybe I misunderstand what you are saying, but you will reach ppO2 of 1.4 with a fO2 of 0.21 at 56.7 msw, which is not outside the realm of possibility, either by accident or stupidity. Of course a OW or a AOW SHOULD not be nowhere near that depth, but we are kidding our self if we think that all divers sticks to the depth they are certified for, I have heard a OW diver bragging about going down to a wreck at 57 meter on his second dive after OW, I have seen AOW divers taking OW divers down to 30+ meters on wall dives where the bottom is more than 100 meters bellow them, needles to say I gave them my two cents and I would never dive with them.

 

[Diver0001]

I had a confusing experience happen last week while diving the Gulf. I'm using my new ScubaPro Luna computer and I was diving Nitrox with a 32% blend. This gave me a MOD of 111'. I have diving well short of this at around the 70-85' range. I have my computer set to 1.4 bar. On the wreck I have plenty of no decompression time but my RBT was frustratingly low. At 85' my computer gave me about 10 min of RBT. It actually went down to 0 and the alarm went off. I still have upward to 20 min of no decompression time and was still at well over half a tank. I did ascend very slowly (to maximize my underwater time more that anything). On the surface I talked to the Divemaster about this and he told me he could make some adjustments on my computer. He put my computer at 1.6bar which now gave me a MOD of 130 still with 32%. On the second dive I had more RBT but still ran out of bottom time well before my no decompression time was up. The alarm didn't go off but I hovered at around the 1-2 min of remaining bottom time. I just kept going higher.

Can some explain how this works? I'm not a complete newbie. I've got 50 or so dives between the N.C. coast and the Gulf. I have never had an issue with my RBT on any other computer. It's just this new Luna that is confusing me. Am I missing a setting?

If you're using the transmitter than RBT takes into account :

a) your NDL.
and
b) your current air consumption and tank size.

If you were getting an alarm before the NDL was getting close then your computer was telling you to ascend because your gas reserve was getting depleted. Your computer, in other words, was telling you what you should have been aware of already, which is that you needed to ascend so you didn't run out of air.

Assuming that what was happening is what I think was happening.

R..

 

[The Chairman]

Thou wilt not surely die! I had to say that since everyone is clamoring that 1.6 is gonna kill you. Chances are: it won't. It won't even come close and you didn't just have a brush with the grim reaper. I set mine to 1.6 and still honor my 1.4 MOD. It's just not that hard and your PDC will not slam you to the depths just because you have set it to 1.6. Rly. You're still in charge of how deep you go, not your PDC.

Now, about reading the manual. It would be a better idea to see if DiveNav has your PDC available as an online class. Here's the link straight to his Dive Computer Training: DiveNav - Products - Dive Computer Training

 

[Water Boy76]

I prefer using my SPG to tell my RBT . Hope you got it sorted out OP.

 

[RJP]

Now, about reading the manual. It would be a better idea to see if DiveNav has your PDC available as an online class. Here's the link straight to his Dive Computer Training: DiveNav - Products - Dive Computer Training

I was going to recommend that, but I checked two things first:
1.) There was no internet meme for that suggestion
2.) DiveNav doesn't have a Luna simulator

 

[The Chairman]

I was going to recommend that, but I checked two things first:
1.) There was no internet meme for that suggestion
2.) DiveNav doesn't have a Luna simulator

I'm sure it's on it's way. Most electronic manuals fall far, far short of being lucid. It's like they've gone out of their way to be obtuse and then they run it through several automated language translators in order to really confuse the heck out of you. That's the great part about ScubaBoard. People often come here to find out what the manual failed to mention or did not explain completely. I love DiveNav's tutorials and am waiting for one on my VTX, even though I pretty much have that figured out. BTW, it came with no manual online or offline.

 

[Hawkwood]

I'm sure it's on it's way. Most electronic manuals fall far, far short of being lucid. It's like they've gone out of their way to be obtuse and then they run it through several automated language translators in order to really confuse the heck out of you. That's the great part about ScubaBoard. People often come here to find out what the manual failed to mention or did not explain completely. I love DiveNav's tutorials and am waiting for one on my VTX, even though I pretty much have that figured out. BTW, it came with no manual online or offline.

The manuals assume you know what the functions are (or are for) and just illustrate how to use or set them. Nothing about understanding those functions.