Need Formula Help - Nitrox

[carolsarinah]

Agree. Stick to 32, follow the rules. Check your tanks! You do not need the formulas. I have a good computer that adjusts for any nitrox mix.

 

[furby076]

I really appreciate your help. While I have 30 dives, many of those was with instructors and all the dives were well within safety limits...couple that with the fact I haven't dove since September and the formulas slip out of my head all too easy. I just need to put myself through drills.

In the meantime, the place I am going to (Cobalt in the Caymans) provides EAN32, and I don't plan on going below 110fsw.

Now to the repetative dive. Does this look correct? Using EAN32 for NAUI:

Dive 1 with EAN32

90 Feet, 30min ADT, ending letter G
Sit Time: 1:47, ending letter E​

Dive 2 with EAN32

70 Feet, Max Time 30 min (blue), Residual Nitrogen 30 (red)
Actual Dive Time 27 min + Residual Nitrogen Time 30 = 57 Total Nitrogen Time
Go to 70 ft, then to 57 min (round to 60 min max time). Ending Letter J
Sit Time: 2:21, ending letter E​

Dive 3 with EAN32

50 Feet, Max Time 151 min (blue), Residual Nitrogen 49 (Red)
Actual Dive Time 30 min + Residual Nitrogen Time 49 = 79 Total Nitrogen Time
Go to 50 ft, then to 79 min (round to 80 min max time). Ending Letter H​

When I do the calculation for Dive 3 I do not include the RNT from dive 1 correct? Just the RNT.

If the above process is correct I plan on using my airplane time to just run numbers.

 

[Doc Harry]

You only need to remember one formula, everything else can be derived from the basic formula:

Partial Pressure = Fraction of the gas x Total Pressure

That's it. One formula. Easy to remember.

 

[GDI]

Here is an Excel spread sheet you can print and stick in your logbook. View attachment 75335

Here is an Excel spread sheet that will do the calculations for you. View attachment 75336

I love using best mix.

First of all keep it simple and what Walter gave you is simple.

I would not fall into that use only 32% or 36% mind set. If you are not matching your gas in the best way possible to the dive you are planning then you are not maximizing the Nitrox gas application advantages. Consider this: On some dives you'll empty a cylinder before your body can realize the advantages of breathing nitrox.

To further simplify what Walter gave you try this I introduce you to Dalton

 

[HJeffreyM]

Most agencies nitrox courses teach the formulas for all mixes and the charts for 32 and 36. I took the PADI course recently and felt I walked away with a good understanding of the formulas. More importantly, I understood the principles of gas partial pressures and their relation to depth. I think the understanding of those principles were the key takeaways from the EAN class.

With that all said, I've never actually seen anyone dive EAN without a computer. I think most agencies also recommend you dive nitrox with a DC. I have an Aeris Elite T3. I tell it what my exact mix is, let it know what I want to use as a Max PPO (I have mine set at 1.2), and it tells me my MOD. During the dive it calculates multi-level nitrogen loading based on the PPO and lets me know with an alarm when I am within 15 feet of my MOD.

So I guess my question is why all the fuss with spreadsheets and calculations? Do you guys all dive nitrox with charts and formulas? C'mon, who's got that slide rule in their BC pocket?

 

[RTee]

Jeffrey...I also dive with a computer but I am not totally dependant on it. If that accessory/tool stops working or is unavailable for whatever reasons I can still enjoy diving using a watch (that I always carry with me), SPG, tables and formulas and be as safe doing it.

Slide rule in BC...very close. It is called a calculator in my logbood binder and a slate on my left forearm with a lead pencil. It is just fascinating to see how easy it is to solve something like the Dalton triangle using those basic tools and /or even more rudimentary methods such as finger/stick and sand/dirt method...keeping in mind that most of the calculations are done pre-diving on terra ferma. :cool2: