O2 load up in 24 hours (EANx question).

[SailNaked]

I have taken basic Nitrox and I am about to take a trip to Bonaire. I was feeling my oats and decided to plan a 5 dive day on Nitrox. the results were that at the end of 5 dives I had reached my 100% O2 limit and may need to sit out for 24 hours.

I think this question may have been asked but I did not see it here.

I have a table that is used to computer O2 buildup over a 24 hour period, It gives no credit for SI and I assume I will basically have continuous diving in Bonaire with no 24 hour gaps for 6 days. I have a pair of dive computers however I'm not the type to rely on them completely.

so my question is this. do I keep track of each dive and roll the 24 hour period for each dive and re compute as the dives roll past 24 hours, or does my loading magically vanish after 24 hours and I start every morning fresh? Is there a different chart for this kind of diving? and I read that the chart is covering us for CNS not pulmonary O2 tox, how many types of O2 tox do I need to track?

Basic question how do I safely track O2 over multiple Eanx dives over multiple days, should I just purchase vplanner now?

 

[Doc Harry]

When I did my deco course I was taught that the half life of CNS toxicity was 90 minutes and I could give myself credit for the surface interval.

Here are some other references that explain it as I learned it. Take internet references with a big grain of salt. You might also go back to the original NOAA publication regarding CNS oxygen exposure limits.

http://precisiondiving.net/blog/2009/02/23/estimating-oxygen-exposure/

http://www.diversalertnetwork.org/medical/articles/article.asp?articleid=35

http://rubicon-foundation.org/dspace/bitstream/123456789/6038/1/SPUMS_V27N1_10.pdf

 

[ianr33]

What pO2 are you planning on using on the bottom?

NOAA limit for 1.4ATM is 180 minutes in a 24 hour period. That works out at 36 minutes per dive at 1.4 Atm. If you are using 32% nitrox they would be decompression dives (36 minutes at 110 feet on 32%)

Anytime the pO2 is less than 1 you can essentially forget about the CNS toxicity,so if you are doing multi level dives most of the dive is not relevant .

Personally I would just stay above 100 feet,do a sanity check on V-Planner and follow my computer.

 

[fdog]

I wouldn't worry about OTU's (pulmonary). IIRC, from REPEX it's 850 OTU's permissible during the first day, and 425 on day 6.

Even doing 5 dives a day, square profile to 66' (50 minutes), with 32%, you'd only total 240 OTU's per day.

As for CNS, again assuming square profiles to 66' and 50 minutes with 32%, you'd be totaling 250 minutes per 24 hour period at a ppO2 of ~1, within the 24 hour limit of 300 minutes. So in this case you'd be using a total of 83% of the allowable CNS clock.

IIRC the sand is at about 105' at the Hooker, the deepest typical dive for recreational divers, and doing this dive (and 4 other dives at 66') would push you to 90% of your daily CNS clock.

Note these are pure daily totals as NOAA ascribes to. The generally used surface decay (which I've yet to see a good study supporting its use, although we all use it) would imply that you'd end a typical day at 25% of the CNS clock. Overnight it would drop to ~1%.

So go dive and have fun. It's good that you are considering these things, but for recreational diving on Bonaire it's a non-issue as long as you stick with 32% nitrox.


All the best, James

 

[fdog]

I have taken basic Nitrox and I am about to take a trip to Bonaire. I was feeling my oats and decided to plan a 5 dive day on Nitrox. the results were that at the end of 5 dives I had reached my 100% O2 limit and may need to sit out for 24 hours.

I think this question may have been asked but I did not see it here.

I have a table that is used to computer O2 buildup over a 24 hour period, It gives no credit for SI and I assume I will basically have continuous diving in Bonaire with no 24 hour gaps for 6 days. I have a pair of dive computers however I'm not the type to rely on them completely.

so my question is this. do I keep track of each dive and roll the 24 hour period for each dive and re compute as the dives roll past 24 hours, or does my loading magically vanish after 24 hours and I start every morning fresh? Is there a different chart for this kind of diving? and I read that the chart is covering us for CNS not pulmonary O2 tox, how many types of O2 tox do I need to track?

Basic question how do I safely track O2 over multiple Eanx dives over multiple days, should I just purchase vplanner now?

Yes.

so my question is this. do I keep track of each dive and roll the 24 hour period for each dive and re compute as the dives roll past 24 hours, or does my loading magically vanish after 24 hours and I start every morning fresh? Is there a different chart for this kind of diving? and I read that the chart is covering us for CNS not pulmonary O2 tox, how many types of O2 tox do I need to track?

Basic question how do I safely track O2 over multiple Eanx dives over multiple days, should I just purchase vplanner now?

No.


All the best, James

 

[RJP]

So go dive and have fun. It's good that you are considering these things, but for recreational diving on Bonaire it's a non-issue as long as you stick with 32% nitrox.

Agreed - my buddy and I did 5/6 dives per day using EANx 32% in Bonaire last year and according to my computer we never got into/near the "red zone" on 02 exposure.

As fdog and others have mentioned there's really nothing deeper than 100' or so worth seeing in Bonaire.

Plan your dives, watch your computer, and have fun!

 

[SailNaked]

thanks that will put my mind at ease somewhat. I will still track it for giggles and practice, but good to know I am not likely to be in trouble if I mess it up. I was playing with vplanner and it seems to say I am fine also for the planned depths of <100 and at least 1 hour SI with 2 for lunch etc. for giggles I tried dives X 5 @ 90 and 36% and got to 45% CNS. (270 OTU). unless I get bigger tanks I am not going to hurt myself.

 

[ianr33]

I played around with V planner myself in a similar way.

Came to the conclusion that diving Al 80 tanks with 32% ,not going into deco and keeping the pO2 below 1.4 it is impossible to exceed CNS Oxygen limits.

Have fun in Bonaire

 

[jscott099]

Here is some actual data from a recent trip my girlfriend and I did in Bonaire: In 7 days we did 42 dives (yep, we dive , dive, dive, and sleep). All but one were 32%. Depths ranged from 50 to 100 ft. Dvie times averaged 45 minutes each. Used Suunto Cobra and Uwatec Smart Z dive computers. By day 5 we started to see OLF's hovering around 75% by the end of the day. Oxygen loading neer became a factor for us.

 

[TSandM]

Your question has been thoroughly answered, but I just wanted to say kudos to you for thinking about this beforehand. Considering possible problems BEFORE diving is a great attitude to have.