Nitrox for shallow water artifact diving??

[Bob DBF]

Conclusion: the Navy tables allow unlimited 100-minutes dives to 25 ft, using SI of 10-52 minutes.

But one must realize that the Navy will be conducting the dive using surface supplied air, a tender, diving officer, and have a chamber on deck, should they screw the pooch.

An earlier quote by Duke Dive Medicine in this thread.

I have a good friend who has treated multiple working divers for DCS from roughly that depth and bottom time. They were extreme sawtooth profiles, but they still defied traditional thinking about the possibility of getting

The Navy tables don't guarantee your safety, they are guidelines for proffessional Navy Divers making working dives.

 

[Akimbo]

But one must realize that the Navy will be conducting the dive using surface supplied air, a tender, diving officer, and have a chamber on deck, should they screw the pooch.

I completely agree with your basic point and would like to add that they get frequent diving medicals, are paid to stay in shape with PT on duty, and are very well trained and supervised.

For clarification, a dive this shallow does not require a diving officer or chamber on deck. Naturally there is a whole chapter in the US Navy Diving Manual Revision 7a to help figure it out: Chapter 6, Operational Planning and Risk Management, starting on Acrobat page 301

However, IMO some of the things they do require are very similar to what every recreational diver should do (red emphasis is mine):

---

6-5.1.3 Emergency Assistance. It is critical to coordinate emergency assistance before
an operation begins. Three types of assistance may be required in any diving
operation:

• Additional equipment, personnel, supplies, or services.
• Clarification, authorization, or decisions from higher command.
• Emergency assistance in the event of a diving related illness or a physical illness/injury.

The location of the nearest recompression chamber shall be identified and the
chamber operators notified before the operation begins. The location of the nearest
Undersea Medical Officer and medical facility shall be located and notified. If
the duty chamber maintains an on-call or on-duty UMO watch bill, then there is
no need to separately contact the UMO prior to the dive. Sources of emergency
transportation, military or civilian, shall be established and verified.

Edit: Of course chambers on deck are required when there is a reasonable possibility that decompression may be required.

 

[Bob DBF]

I completely agree with your basic point and would like to add that they get frequent diving medicals, are paid to stay in shape with PT on duty, and are very well trained and supervised.

For clarification, a dive this shallow does not require a diving officer or chamber on deck. Naturally there is a whole chapter in the US Navy Diving Manual Revision 7a to help figure it out: Chapter 6, Operational Planning and Risk Management, starting on Acrobat page 301

However, IMO some of the things they do require are very similar to what every recreational diver should do (red emphasis is mine):

---

6-5.1.3 Emergency Assistance. It is critical to coordinate emergency assistance before
an operation begins. Three types of assistance may be required in any diving
operation:

• Additional equipment, personnel, supplies, or services.
• Clarification, authorization, or decisions from higher command.
• Emergency assistance in the event of a diving related illness or a physical illness/injury.

The location of the nearest recompression chamber shall be identified and the
chamber operators notified before the operation begins. The location of the nearest
Undersea Medical Officer and medical facility shall be located and notified. If
the duty chamber maintains an on-call or on-duty UMO watch bill, then there is
no need to separately contact the UMO prior to the dive. Sources of emergency
transportation, military or civilian, shall be established and verified.

My knowledge is dated, when I was in the navy had diving barges all over the place. Two or three divers, a diving officer doing double duty somewhere on the base (usually with subgroup if there) and a recompression chamber on board.

I believe they were prepositioned for harbor clearance back in the days of the 1000 ship Navy.

 

[Akimbo]

My knowledge is dated, when I was in the navy had diving barges all over the place. Two or three divers, a diving officer doing double duty somewhere on the base (usually with subgroup if there) and a recompression chamber on board.

It may have been that this group had a chamber on their barge anyway (common) and had a DO assigned to the diving locker. There may also be a requirement for a diving officer to be present for special work, like on submarines (speculation on my part). For example, the Second Class School in San Diego when I went through had a chamber on the dive boat but a diving officer wasn't required for our qualification dives. The instructors were all First Class Divers, but no Master Divers. There is a ScubaBoard member that can give us more recent information. Ping @ND5342

 

[Bob DBF]

And what makes it interesting to sort out is that the Navy has a habit of qualification trumping rate/rank, so the diving officer need not be an actual officer. The actual DO is somewhere up the chain of command, but not necessary since the divers working have the expertise to cover the job.

 

[yle]

Oh, and there is no empirical evidence that nitrox makes you "feel" better.

And there never will be. Because feelings cannot be measured empirically. That would be like saying there is no empirical evidence that blue is my favorite color.

But it is. And some people feel better when using nitrox. So we should allow those people to feel better, but refrain from telling other divers that nitrox will make them feel better too.

Just like we shouldn't tell new divers that their favorite color should be blue.

 

[100days-a-year]

Having actually

And there never will be. Because feelings cannot be measured empirically. That would be like saying there is no empirical evidence that blue is my favorite color.

But it is. And some people feel better when using nitrox. So we should allow those people to feel better, but refrain from telling other divers that nitrox will make them feel better too.

Just like we shouldn't tell new divers that their favorite color should be blue.

And you my friend have made internet a better place today with that comment.
In about a thousand of those shallow dives fossiling or lobstering I could never tell you the difference but have friends who swore they felt better. Why on Earth would I try to make them feel worse over something so trivial.

 

[tursiops]

Circling back to the original issue -- using Nitrox for shallow water artifact diving -- I feel obliged to point out that if you do 25 ft dives on 32% Nitrox, your equivalent air depth is just 17 ft, so you have an unlimited NDL on the Navy tables, which are the only tables I know of that give you NDLs for such shallow depths. My computers don't have a Plan mode that goes that shallow either.

 

[rx7diver]

Circling back to the original issue -- using Nitrox for shallow water artifact diving -- I feel obliged to point out that if you do 25 ft dives on 32% Nitrox, your equivalent air depth is just 17 ft, so you have an unlimited NDL on the Navy tables, which are the only tables I know of that give you NDLs for such shallow depths. My computers don't have a Plan mode that goes that shallow either.

Well, you'd have to be a bit careful with your accumulated bottom time, though, since the corresponding PO2 is 0.57 ATA. The 24-hour oxygen limit for a PO2 of 0.6 ATA is 720 minutes (= 720 / 60 = 12 hours). Of course, oxygen has a half-life, but still, if your surface intervals are short enough, it is entirely possible that you can exceed the 24-hour oxygen limit.

Even more possible if you're diving EAN36 (rather than EAN32).

ETA: Calculations were made with respect to diving in sea water: PO2 = 0.32(25/33 +1) = 0.5624 ATA.

rx7diver

 

[tursiops]

Well, you'd have to be a bit careful with your accumulated bottom time, though, since the corresponding PO2 is 0.57 ATA. The 24-hour oxygen limit for a PO2 of 0.6 ATA is 720 minutes (= 720 / 60 = 12 hours). Of course, oxygen has a half-life, but still, if your surface intervals are short enough, it is entirely possible that you can exceed the 24-hour oxygen limit.

Even more possible if you're diving EAN36 (rather than EAN32).

ETA: Calculations were made with respect to diving in sea water: PO2 = 0.32(25/33 +1) = 0.5624 ATA.

rx7diver

Good point. So if the OP uses 32% he can do 7 100-minutes dives a day at 25 ft.
Long day.