Nitrox for the PS diver

[NorthWoodsDiver]

as a huge proponent of Nitrox I wanted to here the argument about using it in a public safety divers tanks.

break cost away from the scenario, as everyone knows it costs more. but increased bottom time or probably more importantly shorter surface intervals seems to make nitrox really make alot of sense in the PSD world.

Sure you need a source and an analyzer and I suppose it increases training requirements but...

[TC]

In California CalOSHA still applies to PS diving. No problem using nitrox as long as you have a chamber at the dive site. :(

[mntdiver]

:popcorn:

[1_T_Submariner]

I would think speed of getting in the water would be more important than bottom time.

Also in a lot of locations the diving would not be that deep to worry about it or deep enough that Ox Tox could be more of a worry.

I could be wrong but, just seems like a complication they would not want to add.

Maybe good to have a few tanks around for a longer search for something I guess when there would be more time to plan the profiles etc....

[Gary D.]

Simple answer; Higher % Nitrox takes more dive planning than 21% does. In the PSD world it isn’t a problem for RECOVERY teams. But it could be deadly for RESCUE teams who DO NOT have the option of planning a dive.

Long bottom times should not be done in PSD. Shorter bottom times with more dives should be the norm.

Gary D.

[Anti-Hero]

In California CalOSHA still applies to PS diving. No problem using nitrox as long as you have a chamber at the dive site. :(

Why would you need a chamber at the dive site for Nitrox? We don't use Nitrox, but I've never heard of any Cal OSHA requirements regarding it's use.

I just did a *very* cursory look on the OSHA site and didn't find any reference to PSD or using Nitrox.

[TC]

California Code of Regulations, Title 8, Section 6061. Specific Operations Procedures. (http://www.dir.ca.gov/title8/6061.html)

And please note- I think it's ridiculous too, but there it is.

[DA Aquamaster]

I agree with the distinction between rescue and recovery as with the former time is critical and you never know quite what you are going to get. With the latter greater planning and preparation should occur as the time is available.

On the other hand, how many PSD divers are really qualified to dive below the 110ft (PPO of 1.4) or 130 ft (PPO of 1.6) MOD of 32% or the 120 ft or 140 ft MOD's of 30%? How about the 140 ft or 170 ft MOD's of 26%? At some point there is a depth below which the team's divers are not or should not be allowed to go due to lack of training/skills/experience, narcosis or very short NDL's and that depth then becomes the determining factor for what mix is put in the tank.

I understand not wanting to have PSD's engage in deco diving, but let's say you are attempting a search and rescue in 110 ft of water. Your NDL with air is 15 minutes while you have 25 minutes with 32% offering significantly more bottom time or alternatively greater safety on the shorter dive and/or a shorter surface interval between subsequent dives.

From that perspective, Nitrox is just another potential tool in the tool box.

[DA Aquamaster]

California Code of Regulations, Title 8, Section 6061. Specific Operations Procedures. (http://www.dir.ca.gov/title8/6061.html)

And please note- I think it's ridiculous too, but there it is.
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.

[Gary D.]

My argument is if you’re on a RECOVERY team go ahead and use higher percentages. But to eliminate the chance of someone making a mistake in the confusion of a RESCUE, NO mixes over 21% should be used on a RESCUE team period.

Many times we go from one call to another. We fill off the compressor trailer or directly off the trucks. Way to easy to get mixes fubared and tanks confused.

On the deep dives Rescue becomes Recovery much faster than at shallow depths. If it’s beyond what 21% can do it’s going to be a Recovery and not many searches should be done at the deeper depths unless you have a good target.

Gary D.

[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.

[Lucy's Diver]

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

Why multiple short dives?
We, a surface supply air recovery team, strive for the longest bottom times we can, but our SOP is one dive per diver per day. In less than 30 feet 2-4 hour bottom times are typical. Part of this is that swapping divers on a SSA rig is quite a time investment.
We do use nitrox on dives over 30 feet, but we also have a nitroc compressor so its essentially free.

[bridgediver]

Why multiple short dives?


A few reasons. Mainly diver attention span and logistics. Heres what I mean.

1) attention span. For you commercial guys you're probably focused (or at the very least engaged directly) with what you're supposed to be doing so your mind is "occupied" by your task. With us, we haven't found it yet and with blackwater or even zero vis the mind will begin to wander and we lose concentration. Without full concentration the effectiveness of the search is reduced - may go too fast, not realize what we're touching, get paranoid, depressed that "I'll never find it!" etc.
A good span of attention is of course variable for each person on any given day but a reasonable amount of time can be 15-20min.
As an example, there was a team looking for a drowning victim utilizing long dives. After a time they eventually found the victim in a spot they had already serched once before and it dawned on the tender that handled the diver in that location on the first pass that the diver said he remembered finding a "big ball of mud" (which turned out to be the head of the victim) -- he had found the guy the first time but wasn't focused enough to realize it and kept on plodding along

2) Unknown search plan. We don't really know how long we may be searching. It could be the first dive and it could last the week. If we look at the tables and we want a diver to have say 4hrs of BT he will have much less N2 loading if he does short dives vs. 1-2 long ones. We want to limit our N2 loading because we may need the diver for more dives/days

3) Environmental exposure. We may not be as prepared for long exposures as you guys are. It would be rare to see PSDs with heated suits for example. We may not be in a rested, fed and hydrated state when the call comes in (which would contribute to more heat loss). We could be (and often do) find most calls at the end of our shift or early evening
Also, don't forget that the back-up and 90% ready divers are also going to be subjected to the surface environment before they dive for the duration of the dive (or twice that if its the 90%)

4) Search urgency. Some searches may be urgent (rescue) and others recovery but either way it looks bad if the team needs to "take a break" while little johnny is still in the lake. We should be able to have a diver turnaround of only a couple of minutes and keep the op going while guys rehab as they need it. Unless you're fortunate to have allot of divers we have to cycle through what we have - 4 is optimum.

5) fatigue. With long dives we pretty much have to switch out all 3 divers and tenders after each dive. Time to undress, grab a drink , a pee and redress could be 15-20min depending on the fatigue level - thats allot of time spent not searching at all. Let's say the dive is 1hr, the back-up and 90% are sitting in the wind/snow/rain/sun/bugs (whatever) for that hour then the back-up should be ready to do his 1hr dive - now the 90% becomes the back-up and must sit another hour and will essentially get wet/cold/hot/hungry/dehydrated (need BATHROOM!!) for 2 hrs before he can look forward to a 1hr long dive. Up to 3hrs in his gear he will not be an effective searcher in this state.

6) Rehab. Its a fact that it takes allot of time to rewarm and rehydrate team members if they begin to get chilled. If they get mild hypothermia they are pretty much finished for the day and maybe for a couple of days. Most teams don't have that many members to call upon. The best course of action is to prevent the team from getting cold, dehydrated and tired in the first place. Short dives allow frequent rehab and we don't burn anyone out
*Also, tenders can get cold and tired too


So here's what we do. If we have 4 divers we can cycle each guy through a 20min postion of primary, back-up, 90% ready and rehabbing diver. The longest a guy will be dressed is 1hr before he can take a break and refresh.
If we have 5-6 divers we can rehab each guy longer each hour. We could run an op for 8-10hrs straight without stopping the search - thats allot of searching!
If we have 6-8 divers we can also run 2 seperate searches in this manner doubling our efforts.
It works pretty slick

hope that makes sense

mark