oxygen toxicity calculator

[Bigd2722]

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

just curious

thanx

 

[Basking Ridge Diver]

PO2	Max Single Exposure	Max 24 Hour Exposure
	(minutes)	(minutes)
1.6	45	150
1.5	120	180
1.4	150	180
1.3	180	210
1.2	210	240
1.1	240	270
1.0	300	300
0.9	360	360
0.8	450	450
0.7	570	570
0.6	720	720

You mean like this? I use my dive computer to track O2...

 

[tbone1004]

any decompression computer will keep track of it. If you're doing NDL diving it's pretty impossible to max your o2 clock out. Oxtox is due to free radicals bouncing around, but most if not all computers keep track of it. The Shearwaters get SUPER grumpy when you meet or exceed their limits

 

[ajduplessis]

You have an awful lot of dives under your belt with a Nitrox card, how did you manage up until now?

 

[scubadada]

Computers track O2 exposure in different ways. Oceanic computers use a rolling 24 hour window and the exposure limits from the NOAA table, posted above by BRD. As an example, if you are diving 4 dives per day, there are usually 5, or transiently, 6 dives in your 24 hour window as they are not eliminated until 24 hours after the end of the dive. It is not difficult to approach or exceed the NOAA limits in this case with relatively long dives and relatively rich nitrox. My usual drift dives in Boynton Beach using EAN36 generally give me 20-25% of my exposure per dive. I try to get leaner nitrox mixes to reduce my exposure, especially when diving multiple dives per day for multiple days.

Shearwater utilizes an oxygen elimination half-life of 90 minutes. When on the surface, half your oxygen exposure is eliminated every hour and a half. Assuming they use the same 24 hour limits (and I'm not sure this is true, but would like to know), it would be considerably harder to approach daily limits using one of these computers.

I would imagine different brands use different methods, it would probably be prudent to understand how your computer works. I think Uwatec uses an oxygen elimination half life whereas most or all of the Pelagic Pressure Systems computers use the method I described for Oceanic.

Off to add another 40-50% to my oxygen exposure for this visit......

 

[RJP]

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

just curious

thanx

Not sure how a spreadsheet would be terribly helpful, given that your O2 exposure varies by depth and time over the course of a dive. Unless you're diving/assuming a square profile. If you are, you could run out of 02 limits easily in a day.

Using a Vytec DS and doing 5 nitrox dives a day on liveaboard - and as many as 6/day in Bonaire - I've never come close to hitting OTU limits.

 

[rjack321]

Using a Vytec DS and doing 5 nitrox dives a day on liveaboard - and as many as 6/day in Bonaire - I've never come close to hitting OTU limits.

Try diving a CCR, suddenly its like whoaaa I'm at 90% already??!??

 

[Bigd2722]

You have an awful lot of dives under your belt with a Nitrox card, how did you manage up until now?

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

 

[Basking Ridge Diver]

I used Google - nothing with excel though...

try this http://www.diverclub.ru/File/literatur/Oxygen_Toxicity_Calculations.pdf

or this - http://www.scubaboard.com/forums/advanced-scuba-discussions/334121-cns-calculations.html

 

[PCoetzee]

Buy yourself an IANTD C-3201 table. You can get them from DGX.

1) Write down all the depths and times at various depths on a spreadsheet or piece of paper.
2) Calculate the partial pressure of 02 at ever depth. (ATA * fraction of O2) Example: 30m depth = 4ATA. EAN30 at 4ATA: 4 * 0.3 = 1.2 pp02
3) Look for the various 02 CNS and OTU exposure rates for the various pp02s calculated during step 2 on your C-3201 table and write them down.
4) Multiply the exposure rates by the planned time at the various depths.
5) Add up all the totals and you should now have the total planned OTU and CNS values for your planned dive.

Remember that it is unwise to exceed 80% CNS and not to exceed 300 OTUs within a 24 hour period.

Also take note that your CNS clock has a 90 min half time when out of the water.

---------- Post added June 24th, 2015 at 09:20 AM ----------

PO2	Max Single Exposure	Max 24 Hour Exposure
	(minutes)	(minutes)
1.6	45	150
1.5	120	180
1.4	150	180
1.3	180	210
1.2	210	240
1.1	240	270
1.0	300	300
0.9	360	360
0.8	450	450
0.7	570	570
0.6	720	720

for simple square profile planning when doing no-deco diving you can use the table above.

1) Get you maximum pp02 at the deepest point of your dive. (ATA * fraction of 02) Example: EAN36 at 25m depth: 3.5ATA x 0.36 = 1.26pp02
2) decide what your total bottom time will be. Example: 40 minutes
3) Using the table above: Round your pp02 to the bigger number for conservancy. Example: 1.26 becomes 1,3 pp02.
4) Using the table above: Get the maximum single exposure value for 1.3. (1.3pp02 = 180 min max single exposure)
5) Now simply divide the planned bottom time from step 2 by the maximum from step 4. (40 min / 180 min = 22.2% CNS)

remember to also consider the 24 hour exposure max for planning repetitive dives.

---------- Post added June 24th, 2015 at 09:23 AM ----------

Please remember that there is no substitute for proper training...
If the calculations that I have provided does not make sense to you then seek out proper training from a respected instructor.