Nitrox Common Mixes

[conway400]

What percentage mixtures are you commonly using and why? pros and cons?

Just wanting to learn more about certain limits placed on certifications (32 and 40 being common) and if it matters much to me as a rec only diver.

Thanks in advance! I always learn a lot reading here as we get answers that we didn't even ask for as the threads progress.

 

[TSandM]

I dive 32% exclusively for recreational dives. It's pretty widely available, and gives you a reasonable MOD (111) which is deeper than I want to go, because I'm pretty susceptible to narcosis. It gives a substantial advantage in bottom time as compared with air. All my buddies dive it, too, which means that we don't run into problems with people having different NDLs.

Higher Nitrox percentages will give you longer bottom times, but shallower MODs, which decreases your flexibility to change dive plans or sites, if the one you intended can't be done for some reason.

 

[waterpirate]

For strictly recreational, ndl diving the standard noaa mixes 32 and 36 are common. Your recreational nitrox cert lets you use a mix as high as 40%. Mixes that are leaner will yield you a deeper mod and richer a shallower mod. At shops that fill more than just recreational fills you will see a wider variety of banked gas and choices. 30% is a popular choice for diving in the 130 range.
hope this helps
Eric

 

[Tortuga68]

Best mix. Because it's best

 

[Rainer]

Until your first choice site is blown out and you realize best mix sucks balls when you're stuck on the boat...

Best mix. Because it's best

 

[Dive-aholic]

It depends on the depth at the dive site. You'll find that some shops in certain areas will bank what works best for the sites they normally visit. 32% is a common mix because it's one of the NOAA mixes and is good to 110'. I have limited experience in the Florida Keys, but I've heard 36% is banked there by many shops, which makes sense since many of their dive sites are shallower than 95'. Up in NJ some shops bank 28% because that will get you to 130', the recreational limit.

I use 32% for most of my open circuit diving and 37% for most of my SCR diving (which ends up giving me 32% in the loop).

 

[Mossman]

What percentage mixtures are you commonly using and why? pros and cons?

Just wanting to learn more about certain limits placed on certifications (32 and 40 being common) and if it matters much to me as a rec only diver.

Thanks in advance! I always learn a lot reading here as we get answers that we didn't even ask for as the threads progress.

If your diving is local and you can get custom fills, then it depends on the particular dive profile you're planning. On the other hand, if you'll be traveling to dive, most places that offer nitrox do so exclusively in the 32% flavor (+/- 1-2% when it's actually analyzed). On my last trip in Cozumel, one dive op was able to supply us 32% for the first dive and 36% for the second, and I've been able to occasionally get custom fills abroad (Buddy Dive in Bonaire was one, Truk Odyssey liveaboard is another), but generalizing among dive resorts and liveaboards and dive locales like Bonaire, 32% is pumped about 99% of the time. Florida is an exception because there are as many local divers as tourist divers and lots of local tech divers, so many/most shops do custom fills.

 

[Tortuga68]

Until your first choice site is blown out and you realize best mix sucks balls when you're stuck on the boat...

Leaving aside the point that the OP asked what I use, how is that different to having XX% in your tank and needing a deeper MOD than XX% provides?

 

[Rainer]

Simple. Choose a standard nitrox gas that matches the deepest MOD you'd be willing to dive anyway. For me, that works out to 32%. Past 110', I'd want helium locally anyway. 32% covers *any* dive depth I'd be willing to do on nitrox (1-110').

If I bring 40% for a dive planned to 70', but that's blown out and we end up at a site in 100', I'm screwed (been there, done that once, never again).

There are also other benefits to a standard gas choice: teammates are all on the same gas (so similarly NDL-limited), familiarity with allowable NDLs at various depths / profiles, not having to remix for future trips, ease of blending, ease of gas acquisition, etc.

How is that different to having XX% in your tank and needing a deeper MOD?

 

[djtimmy77]

I am a big fan of 40% for most diving that we do here, but I generally keep on hand in my three tanks a ~32, ~36, and ~40 so I can be flexible with profiles.