Accumulated 02 following a large number of repetitive Nitrox dives over 3 days.

[Lorenzoid]

@Astran , I suspect by asking what certification agency you did your training with @kmarks was probably getting at the fact that at least a couple of different methods for tracking multi-day cumulative oxygen exposure have been developed, and any given cert agency probably doesn't mention all of them. Your computer uses one of them. I don't recall my Nitrox course mentioning any methods specifically; in fact, the instructor likely told me that cumulative O2 exposure is a real thing but isn't something most recreational divers ever have to worry about. As Jack said above, it's rare for recreational divers to exceed these limits. But it's certainly possible if you do many deep-ish dives over a few days using high EAN percentages such as 34 or 36, as you did.

 

[rhwestfall]

@Lorenzoid - yep, that was my experience in training too.... we went over it, but also the idea that "normal" recreational diving wouldn't trigger it....

Having never done a LOB, or really pushed (3 dives a day max), I've never been close...

 

[Lorenzoid]

I've always wondered how much and what kind of diving would be necessary for this to happen..... Never imagined it possible....

and now I know....

I know. It comes up now and then in various threads, and someone always takes the position that it's virtually impossible for a recreational diver to reach the O2 clock limit. I vaguely recall someone cooking up a possible schedule of dives that he claimed would hit the limit.

 

[uncfnp]

I have to disagree to a certain extend in that if you set your computer to a more generous ppO2 limit, say 1.6 and then you dive nitrox, either percentage or depth to that limit, you will hit your daily exposure sooner.

So if you have good air consumption (or big tanks) and dive at or near 1.6 while using a liberal dive algorithm, I could see this happening.

If you set your computer to 1.4 it will take longer to hit the exposure limit.

 

[rjack321]

I know. It comes up now and then in various threads, and someone always takes the position that it's virtually impossible for a recreational diver to reach the O2 clock limit. I vaguely recall someone cooking up a possible schedule of dives that he claimed would hit the limit.

Well this was 3 dives, 6 dives, then 4 dives in 3 days with progressively increasing fO2. Not exactly "best mix" but pretty close.

If the OP had stuck to 32% throughout the whole weekend, the CNS and pulmonary loading from the 6 dives on Saturday would have been much lower and wouldn't have gotten to the alarm state on Sunday. The 96ft dive on sunday definitely wouldn't have been such a big percentage of total O2 capacity.

 

[Diver below 83]

Maybe the OP just isn’t Nitrox certified? I don’t see what the hesitation of mentioning the agency you got your certification with otherwise. Your profile states your padi but nothing about nitrox. Also you mentioned hundreds of dives but your profile says 50-99? I’m NAUI Nitrox. No issues stating that. The more information you provide the better the answers you’ll get.

 

[JackD342]

I have to disagree to a certain extend in that if you set your computer to a more generous ppO2 limit, say 1.6 and then you dive nitrox, either percentage or depth to that limit, you will hit your daily exposure sooner.

So if you have good air consumption (or big tanks) and dive at or near 1.6 while using a liberal dive algorithm, I could see this happening.

If you set your computer to 1.4 it will take longer to hit the exposure limit.

I read your post 4 times, and I am not clear on what you are disagreeing with.

But just in case there is some confusion on the algorithms...

The 24 hour limit is not the same as the the various liberal or conservative algorithms for depth and time limits on a single or series of dives. While there may be more than one variation on the exposure limits in use, (DSAT, NOAA, SSI, etc.) it is a far more absolute measure - exposure at a given partial pressure for a given period of time is known and calculated by your computer, nothing at all like the fuzzy theoretical tissue compartment loading, micro bubbles, etc. tracking that is done by the base algorithm.

 

[uncfnp]

I read your post 4 times, and I am not clear on what you are disagreeing with.

But just in case there is some confusion on the algorithms...

The 24 hour limit is not the same as the the various liberal or conservative algorithms for depth and time limits on a single or series of dives. While there may be more than one variation on the exposure limits in use, (DSAT, NOAA, SSI, etc.) it is a far more absolute measure - exposure at a given partial pressure for a given period of time is known and calculated by your computer, nothing at all like the fuzzy theoretical tissue compartment loading, micro bubbles, etc. tracking that is done by the base algorithm.

Hi Jack. Let me try it differently. The OP is confused by 3 different computers telling him he had reached his limit. My post is an attempt to show how this prehaps might happen to a recreational diver that dives at a higher ppO2 than commonly used by recreational divers, 1.6.

My slight disagreement is to the posts that say computer settings do not matter. It does if the diver then dives to that limit. If the diver sets his computer lower, say 1.4 and then dives under that limit it will be harder for him to hit the 24 hour limit.

The reference to his liberal algorithm, if such it was (Oceanic), it will allow said recreational diver a longer dive time (longer ndl) letting the diver hit up against the 24 hour limit. Again, especially if said diver is diving to 1.6.

 

[rjack321]

Hi Jack. Let me try it differently. The OP is confused by 3 different computers telling him he had reached his limit. My post is an attempt to show how this prehaps might happen to a recreational diver that dives at a higher ppO2 than commonly used by recreational divers, 1.6.

My slight disagreement is to the posts that say computer settings do not matter. It does if the diver then dives to that limit. If the diver sets his computer and then dives under that limit it will be harder for him to hit the 24 hour limit.

The reference to his liberal algorithm, if such it was (Oceanic), it will allow said recreational diver a longer dive time (longer ndl) letting the diver hit up against the 24 hour limit. Again, especially if said diver is diving to 1.6.

I don't know of any computer that allows a diver to change the O2 toxicity settings.
Shearwater allows you to change the percent CNS that triggers a warning. But the actual limit is the same.

 

[dmaziuk]

The OP is confused by 3 different computers telling him he had reached his limit.

That sums it up quite nicely I think.