Why not air?

[AndyNZ]

I assure you, at 25', I don't need that 20% credit.

I agree - but if I didn't have to pay huge amounts for it and could get it consistently, I'd probably use it!

Rather than the depth issue, it was more addressing the "Why only 32%" portion of the OP.

 

[Rainer]

And I'd probably dive it then, too. The fact of the matter is, it is a pain to get here (logistics and cost). Given these factors AND the shore dive topography, air is often a good local choice. Especially when the closet dive shop gives air away for free.

When I shore dive back in San Diego or LA, 32% makes a lot more sense. The sites are just a lot deeper. And at least in SD, getting 32% isn't very hard at all. Having a single standard gas for a range of recreational depths also makes a ton of sense (for the reasons GUE teaches).

 

[jefffalcone]

Thanks for all the responses guys. It sounds like a lot of people are thinking along the same lines as me. They cram a lot of information into a short period of time in a fundies class. I asked about this, but didn't really get a satisfactory answer.

 

[allenw1972]

During my fundies class, we were told to dive air. I hear the DIR police sirens now. We will never see that instructor again.

Standard gases are all well and good... and even better on deeper dives, but there seems to be reality, and a GUE target on many things.

For the record, I have a much higher percentage of EAN32 dives than EAN21 dives over the past year.

 

[rainman_02]

Are there not advantages in terms of simplified dive planning? I've have to go back and look at my fundies stuff, but all the deco-on-the-fly, minimum deco, CNS "guesstimates" etc are based on a 32% mix. I'm sure you could re-work out those guesstimate rules for air, but whether they be easy to remember I'm not sure.

You might want to review those notes. The 32% numbers come from air...adjusted for your EAD credit.

100:20 becomes 100:30 etc...

 

[Craig Winnerman]

We were taught air is for tires.

Actually save the nitrogen for the tires. Nitrogen is better than air for tires and you surley do not want to breath the nitrogen

 

[mer]

The underlying principle is that in GUE we are thinking divers. The reasons for the gasses choose are:
1. Acceptable PPO2 (Unbendable rule: 1.2 max working, 1.4 contingency max working, 1.6 max resting deco)
2. Acceptable narcotic depth - remember this is a combination of PPN2 and gas density causing CO2 rentention - (Unbendable rule: END shallower than 100')
3. Familiarity and personal history with minimum deco limits and/or decompression schedules on each of the standard gases

What you choose to breathe must take the above factors into account.

In addition, it is hard to get Nitrox in the Boston area, so I completely understand that problem. Another is logistics of what's in your tanks. As a Tech 1 diver, I tend to have 21/35 in one set, 30/30 in another, and 32 in a third set of doubles. I typically shore dive on a leftover fill of 32. I generally won't fill a set with air, cause knowing my luck, I'll get blown out of that shallow/shore dive, then have to dump and refill for a wreck dive. Air may be an acceptable option in the pool or shallow bug dives (30'), but around 50' the minimum deco limits for air and nitrox32 diverge. So I generally just find it easier to dive nitrox all the time.

Why not best mix:
We don't choose different flavors of nitrox (28, 36 etc). As a Tech 1 diver, I have a lot of personal experience on 32, 30/30 and 21/35. I know what the deco looks like and I know how myself and my regular buddies react on those schedules. If there were many other gas options, our experience would be diluted over many more deco schedules.

Bottom line is, however, that compromising sucks. If all of us actively diving in Boston DEMANDED nitrox, the availability would go up and the price down.

 

[Rainer]

Mer, this probably isn't the right thread for it, but as much as *I'd* like to see nitrox availability go up and price down, I'm not holding my breath. What's the demand? A few GUE divers? Boat divers? The reality of local diving here is that most divers are shore divers, and our shore dives are very shallow. There just aren't that many sites where 32% makes any sense. Also, those of us closer to Boston have access to free air. If I need to dump it to refill my doubles with 32%, no big deal, I'm out nothing. With free air, nitrox would have to be wicked cheap. Again, for any recreational boat dives, it's what we bring (but we mix our own...), and we certainly don't bother with that "best mix" crap. I just don't see this changing any time soon (maybe PG will eventually start pumping nitrox, but then again, they've been saying that for years...).

 

[b1gcountry]

1. Acceptable PPO2 (Unbendable rule: 1.2 max working, 1.4 contingency max working, 1.6 max resting deco)

EAN32 reaches a PPO2 of 1.2 at 91'. Doesn't a MOD of 100' for EAN32 break their own acceptable PPO2 levels?

Tom

 

[Rainer]

EAN32 reaches a PPO2 of 1.2 at 91'. Doesn't a MOD of 100' for EAN32 break their own acceptable PPO2 levels?

Tom

Shhhh. GUE ignores that. As do all GUE divers I know (myself included...).