Mixes >40% O2?

[bleeb]

Trying to understand this newfangled Oxygen thingy, mostly out of interest rather than any immediate plans to dive with it.

Other than 100% and maybe 80%, what other mixes do people routinely use with O2 > 40%? Or do you not use specific mixes?

 

[gconner]

For deco I use 50% & 100%. I know some people use 80% as well. I've never seen anyone use anything else.

-- Gary

 

[lowviz]

Hey, bleeb!

Start here. I particularly recommend anything by Shreeves.

Bibliography: Nitrox

 

[rongoodman]

50% and 100% are standard GUE mixes here and are used by many other tech divers too. I often see references to 32% and 80% on the UK sites.

 

[Shcubasteve]

An argurment for the use of 80% is that, without a booster, the max pressure you'll ever get is 2250+- out of a FULL o2 cylinder. At 3000 PSI, you have to add 2220psi of o2 then top up with air to get 80%. You could spend tons of $$$ on an oxygen booster, or dive 80% with a standard compressor.

 

[PfcAJ]

You don't really need a "full" bottle of o2 for most dives. Even an al40 with ~2k in it is enough for 30-40mins at 20ft with a reasonable reserve.

 

[String]

Trying to understand this newfangled Oxygen thingy, mostly out of interest rather than any immediate plans to dive with it.

Other than 100% and maybe 80%, what other mixes do people routinely use with O2 > 40%? Or do you not use specific mixes?

Some agencies specify standard gases so you have to use those, others customise for each dive.

If you exclude trimix deco gases then id say the most common nitrox ones by a long way are 50% and 100%. 80% is also common.

If you're tailoring a dive profile specifically you can end up with 75/70 or even 60% mixes and its entirely personal preference if you want to go all that way or not.

I like 50/100 but i have used 70, 90 and other mixes before now - in some cases you dive what they can blend which isnt always the same as what you ask for or would like. O2 isnt in that abundant supply in some areas, booster pumps aren't and so on.

32% is a fairly common non-deco nitrox mix used as a bottom gas. You can/do use 32% as a deco gas but with the MOD of 40m its normally associated with a deeper trimix dive (ive used it but with He in the mix too)

 

[Scott L]

I am guessing the OP is referring to NDL dives. While on the question, are there folks who utilize >40% for shallow reefs, etc.?

 

[Peter Guy]

While on the question, are there folks who utilize >40% for shallow reefs, etc.?

I'm often tempted to use 50% when I'm teaching an OW class since I tend to have to go up/down so often!

 

[rigdiver]

I've used >40% specifically for coral spawns. Pretty neat to get 90 minutes at depth without any deco.