oxygen toxicity calculator

[EFX]

There are spreadsheets for just about everything. Does anyone have one for tracking/calculating oxygen toxicity?
just curious. thanx

I'm working on it. I've added the pulmonary oxtox to my tissue compartment calculator which BTW is a spreadsheet. I haven't posted this version yet because I want to include the CNS calcs which I am working on now.

 

[rjack321]

I can certainly track my exposure, the question was how to calculate it ahead of time.

100/allowable mins at that ppO2 = CNS% per min

e.g. plan for a 60min 32% dive
20mins at average 100ft (ppO2 1.3) = 100/180 * 20 = 11%
40mins at average 60ft (ppO2 0.9) = 100/360 * 40 = 11% (coincidentally)

Total = 22% for this 1hr dive

If repeating after 2hr surface interval...
90 min half time
120/90 = 1.3 half times (for all practical scuba math purposes)
1.3 * 0.5 = 0.66 of CNS load disappears. 33% remaining

0.33 * 22% = 7.25% of CNS load needs to be accounted for in dive 2. This is basically nothing on recreational OC. The only way this starts to become an issue is with accelerated deco at ppO2 1.6 or CCR diving where your at 1.2 or 1.3 regardless of depth for the whole darn dive.

 

[KenGordon]

If repeating after 2hr surface interval...
90 min half time
120/90 = 1.3 half times (for all practical scuba math purposes)
1.3 * 0.5 = 0.66 of CNS load disappears. 33% remaining
.

1.3 half times should be calculated by 0.5 to the power of 1.3. By the method above two half times would leave no CNS rather than the actual quarter.
0.5 ^ 1.3 = 0.41 so 41% remaining.
Typically it is taught to only consider whole half times which avoids the fractional powers.

 

[RJP]

I can certainly track my exposure, the question was how to calculate it ahead of time.

V-Planner

 

[tursiops]

I can certainly track my exposure, the question was how to calculate it ahead of time.

No, that isn't what the question was. It is a good question, but not what you originally asked. It may have been what you wanted to know, but it was not what you asked.

To add to what RJP said earlier, I've (for fun) tried using the PADI Nitrox tables to see if I can construct an NDL dive series on 32% or 36% that will hit the oxtox limits. I can sort of get there using 36%, but cannot with 32%. I was doing things like NDL dives to the MOD for 36%, normal surface intervals, then doing it again. So on dive one to 90 ft for 40 mins you pick up 30%; 1h SI lets the next 90 ft dive be for only 21 mins, so you only pick up 15% on that dive. So 3 more 21 min dives to 90 ft, with a 1h SI in between, gives another 45%, for 90% total. So, using 36%, 5 consecutive dives to 90 ft, all to max NDL, and 1h surface intervals, gets me to 90%.

Doing the same strategy with 32%, first dive is to 110 ft for 25 mins, giving 20% O2. 1h SI, second dive can only be to 110 ft for 13 mins, giving 10% O2. 7 more NDL dives like that and I'm at 100%, but I had to do 10 dives totalling 142 minutes BT plus 9h of SIs, for a LONG day!

 

[RJP]

I've (for fun) tried using the PADI Nitrox tables to see if I can construct an NDL dive series on 32% or 36% that will hit the oxtox limits.

Dude, you gotta get out more!

 

[PCoetzee]

Here is a file I built that includes all the CNS as well as OTU calculations. I have balanced the results with the IANTD C-3201 table and added a simple CNS calculator for you on the second sheet:

 

[RJP]

I can sort of get there using 36%, but cannot with 32%.

That's assuming you're staying within recreational NDLs, and only diving a single gas.

 

[Basking Ridge Diver]

Here is a file I built that includes all the CNS as well as OTU calculations. I have balanced the results with the IANTD C-3201 table and added a simple CNS calculator for you on the second sheet:

View attachment 211294

Once you change your depth to 50 feet it throws an error - 20, 30 and 40 foot depths are ok...

I did not validate values just if it was working...

 

[PCoetzee]

My spreadsheet is metric and not imperial. I'll add an excel convert function and republish a bit later.