Nitrox for the PS diver

[bridgediver]

Good question
I'll be echoing allot of what has already been said but bear in mind the vast majority (over 90%?) of teams will never go below 60ft - allot won't exceed 30ft.
We don't want bottom times longer than 20min even if the tissues allowed it - the concentration level of the brain and environmental exposure maxes out about that point anyway when doing multiple dives - ie up to 6-8 a day. If we keep the dives short we CAN do that many dives safely in a day. Nitrox doesn't give you anymore MULTIPLE dives which is a big consideration for rescue or recovery. Once we max out a diver he's done for the day and we need to find a new one

Unfortunately cost is always a factor for PSD but so is time to train. It would take allot of effort to train a team (and maintain competency!) in handling nitrox. Time and money that could be spent in other areas.

There is always a multitude of team members that handle one's gear. Both for checks and set-up. many are non-divers. Too much can go wrong without COMPLETE understanding of nitrox ie - bad mixes.

Most of the time it is the tenders that handle the dive profiles, monitor SAC, bottom time, depth and especailly the search pattern etc (because the diver can't see). Tracking O2 exposures would be a nightmare.
Also, we're supposed to analyze gas before the dive which won't happen in PSD

Basically, when dealing with these shallow depths and times (less than 60ft and 20min) there are many more complications to using nitrox than the benefit it provides

 

[tc]

The regs make perfect sense in terms of "mixed gas" if it is defined as mixes such as heliox or trimix, but the intent clearly is directed at deep diving, not dives shallower than 100'.

I'd be interested in a legal opinion as to whether "mixed gas" applies to nitrox that is by definition intended for shallow water use - unlike mixed gases utilizing helium. I supect the regs and underlying statute pre date the common use of nitrox mixes and that nitrox has just been swept up in the "mixed gas" terminology that used to be synonymous with helium based mixes with no regulatory intent to ever include nitrox in this category.

Then again, it is the PRK and getting them to unforbid anything they've already forbid, intentional or otherwise, is a daunting task.

We also questioned this point directly with them- Their definition of mixed gas is anything other than compressed air.

 

[Anti-Hero]

That's interesting, in a California nonsensical way.

 

[bridgediver]

Our standards in Canada sound like the same - we need a chamber on site for mixed gas also.

What allot of sport divers don't realize is that when doing PSD deep the diver is not just doing deep dives. He is in most cases solo due to zero vis. This makes gas supply a nightmare on scuba - you have no buddy to rely on if something goes wrong in this entanglement prone environment. Where a single 80 may be enough for a buddy team doing a sport dive to 100ft it certainly pushes if not exceeds the limits for PSD. The standard 19cuft pony bottle used for the normal depths (less than 60ft) also needs to be bigger - at least a 30cuft; maybe even a 40cuft.
So, even at a "measly" 100ft dive this is turning into a technical very gear intensive dive and we aren't even addressing what the back-up diver and 90% ready diver needs to do and what they need to carry.

This is why you'll usually see PSD work at these depths done with SSA. Fortunately this equipment is becoming more portable and economical so they are becoming a reality. Training and equiping a team for what would be described as "tech diving" so they can do ops to 100ft would be about the same as a SSA system.
In the PSD environment SSA is safer than any deep scuba procedures.

Again, nitrox (for scuba) doesn't give us any benefit

 

[WolfEl]

I really don't see a pressing need for PS divers to use Nitrox. I love to use Nitrox normally in recreational diving, especially on extended boat diving trips.

In my experience as a PS diver, we had very few 'rescue' dives, except for our work on the Unlimited Hydro races, when we did that.

As for recovery work, I really don't see why anyone would want to spend the extra money on Nitrox and/or mixed gases, unless there was a defined reason to use them. Given such a reason, and using a dive plan that incorporated such gases in the plan, I would say go for it.

That said, I think most PS divers should be trained in the use of Nitrox and/or mixed gases, especially where such incidents occur fairly often, that would dictate there use.

 

[NorthWoodsDiver]

Those are some expected responses and some good points I didn't think about.

I also overlooked mentioning that I come from a recovery team, by the time they call us the fire department and other SAR personal have already done their best. This I suppose skews my view as we have plenty of time to plan and prepare of for the dive operation. Our divers are limited to 20 min or 1000psi depending on depth, water temp, and the diver. Our team works under the sheriff's dept so they call the shots and limit us to searches in 60' or shallower unless we have a good hit or a known positive location in water up to 100' deep.

One of the biggest issues we have is numbers. call outs, training, or public events never seem to generate more than just a couple divers and often its the same people. That was the primary reason for me thinking nitrox would be a good idea. Having only 2 or 3 available divers on a large search area or location with multiple hits to check out may mean putting those divers in the water several times each and if the depths are below say 40' at 20 min per dive thats quite a bit of loading going on.

So for the reasons using the appropriate mix, assuming it was available, seemed to me like a good option. Although I do agree with the cons to the scenario as well like cost, planning, training, availability, legality (except for the chamber part), etc.

Thanks for the input.

T

 

[bridgediver]

Our standards in Canada sound like the same - we need a chamber on site for mixed gas also.

I need to remove this from my post as it is wrong. Our CSA's have no such restriction - my mistake, sorry.

We need a chamber onsite only if we exceed NDL's or 130ft

thanks Ditch

 

[1_T_Submariner]

I also overlooked mentioning that I come from a recovery team,

Not to be a jerk but, you overlooked that you come from a recovery team? Hmm are you sure you should be diving without special supervision or something. Is it a memory problem or were you trolling?

Good disscussion, just strange you "overlooked" mentioning it.

 

[DA Aquamaster]

We also questioned this point directly with them- Their definition of mixed gas is anything other than compressed air.

Hmmm...I'm gonna call them and let them know that air is a mixture of 21% Oxygen and 79% Nitrogen and is consequently a mixed gas.

 

[tc]

Hmmm...I'm gonna call them and let them know that air is a mixture of 21% Oxygen and 79% Nitrogen and is consequently a mixed gas.

They'll probably believe it too.

Great, now I've got to start chamber shopping.