2 Tank Dive -- Nitrox Use

[dpspaceman]

Wanted to get a sense for folks preferences...
Two tank dive
1st dive: max depth 110
2nd dive: less than 60 feet.

My thought was 32% for first dive, 40% for second.
How do you guys feel?

 

[BRT]

First dive is obvious at 32%. Second dive you probably will not approach your NDL with 32% unless you have a short surface interval. I only pump 32% but if I was picking nits then I'd have the second tank full of 40%. Don't believe I'd gain anything.

 

[rongoodman]

I would just use 32% for both.

 

[Altamira]

Dove a week at Bonaire a couple of years ago at the Habitat, and all the tanks were filled 32%, and some folks dove 4-5 times a day. Did not seem to be an issue.

 

[Doc Harry]

One day of diving? Then it doesn't matter, use 32% for both, or as you say.

Repetitive days of diving, with perhaps a third or fourth dive later that day/night - I'd use 32% and 40%.

 

[Steve_C]

Are you sure that your dive will go. I fill my tanks and then depending on weather the next dive may or may not be where I want to go. I also like to keep the PO2 at 1.3 or below. I am an old guy. So usually just have 31%. (Ask the shop for 30 and they usually give me 31 or 32). Covers me no matter where the boat goes.

 

[BertStevens]

It depends on what is available. Some places only mix 32%. Some only mix 32% or 36%.

If any mix is available, then I'd get best mix for the planned depth. If not, then I'll take best available.

 

[Reku]

I'd probably do 32% for the first dive and 36% for the second - because most places have either 36 or 34.

 

[AdivingBel]

On a 2 tank day and the second dive is multi-level, less than 60 ft. max (typical shallow reef bimble 2nd dive), I would dive 32 on the deep dive, take a reasonable SI, dive air on the second, and splurge for an extra beer for myself and my dive buddy over dinner while discussing our fun day of diving. YMMV.

 

[CuzzA]

There may be more to consider. Without too many details about the dives it's hard to say. On my boat I keep an aluminum 80 full of air. If I didn't do that I would have both tanks the same mix in the event after the first dive I needed to go back down to retrieve something/someone whether it be an emergency or not. I wouldn't want to be handicapped by a MOD on my second tank. So since I have a tank with air, generally speaking I would be fine with different mixes in my other tanks for different depths.