Question on Nitrox use with repetitive diving

[Hatul]

I plan a 5 day, two dive per day, Cozumel vacation. The first dive is generally the deeper at 90 ft or so and the second shallower 60 ft or less. If I plan one Nitrox dive and one air dive is it better to use the Nitrox on the first or the second dive?

 

[OtherHalf]

Why are you planning one of each, instead of doing nitrox on both dives? I would want the nitrox on the deeper dive to extend my time. I generally figure I'm more likely to run out of air at 60 before hitting my NDL, but more likely to enter deco at 90 before running out of air.

 

[Belmont]

Both dives, you only live once!

Otherwise I would think on the second dive.

You can then use a higher percentage of oxygen.

There are some tissues that absorb nitrogen faster than others.

Higher O2 on the second dive would even help you get rid of some nitrogen accumulated on the fast absorbing/releasing tissues saturated on the first dive.

Also give you a more efficient release of nitrogen on the last minutes of your dive, eg: safety stop.

 

[Hatul]

I should add that Nitrox only comes in Al 80's and air can be had in al 80 or al 100 (Dive with Martin). The reason for buying just one Nitrox per day is simply to save money, being a cheapskate.

 

[darushin]

Depends on your mix. If you are less then 70 ft and can get 36% or higher then use it on the second dive. Otherwise use it on first.

Sent from my HTC One using Tapatalk

 

[kelemvor]

I agree with darushin. Get 36% for the deeper dive. Dive with Martin supplies either 32 or 36 according to their website. The site says you have to order in advance for trox.

 

[Centrals]

1. It is all depend on the topography of the site.
2. If it is a square profile eg. wreck(30m max) then I would use Nitrox.
3. If it is multi-levels then I would use Nitrox on the 2nd dive to aid the off-gassing.
4. If I am a cheap charlie then I would use EAN21 on both dives.
5. Surface interval is also a important factor to consider, the longer the better.

 

[knotical]

The first dive, as long as you don’t exceed your MOD.

If you use Nitrox on your first dive you benefit from a reduced nitrogen loading on that first dive, and you enter the water for the second dive with a lower nitrogen load than otherwise. If you use Nitrox on your second dive, only that second dive benefits.

 

[Superlyte27]

The reason for buying just one Nitrox per day is simply to save money, being a cheapskate.

That's a great approach to diving.

 

[Tigerman]

Hands down the first, deepest dive is where Id use nitrox if I could have it for only one. 60ft you can stay for 55 minutes on air (on a square profile) if you're fully offgased. At 90ft only 25 minutes... With 36% you can stay at 90 ft (28 meters is the closest I have on my metric rdp) for 40 minutes.. Thats a BIG increase (probably bigger than you need on an al80)


What I do in reality is get an "all the nitrox you can breath for $X" package though and use it on all my dives. Normally the widely available 130ft compatible 32% kind..