Diving using Nitrox?

[Twiddles]

There are now over 9 million certified divers. Most of whom are classified as recreational divers, who dive with only an OW card, who dive on vacation only etc, etc, etc. Who do not hit NDL but rather suck the tank dry like a Kirby on a throwrug.

Adurso Im glad you asked =),

Step 1- OOA Regulator Exchange & Problem Assessment at Depth
time at depth (in minutes) X depth (ata) X RMV of 2 divers (working RMV) =

Step 2- Ascent from Depth to 1 Stop
time to ascend (in minutes) X avg depth (max depth to stop depth, in ata) X RMV =
Step 3- *Stop (1 minute deep stop or 3 minute safety stop)
stop time X stop depth (ata) X RMV =

Step 4- *Ascent from 1 Stop to Safety Stop (max depth deeper than 80fsw)
time to ascend X avg depth (stop depth to safety stop depth) X RMV =
Step 5- Safety Stop
time at stop X stop depth (ata) X RMV =
Step 6- Ascent from Safety Stop
time to ascend X avg depth (stop depth to surface, ata) X RMV =

Step 7- Total Gas Used
Add steps 1-6

Step 8- Convert to PSI
CuFt of gas needed / rated volume of tank / rated pressure of tank =
Step 9- Add 200psi for Reserve

Add 200 to step 8 for total Rock Bottom

**EDIT** Above information was obtained from Understanding Gas Management by Bob Bailey.

Punch in 70' see how well you do, keeping in mind your breathing at 70' for 35 minutes (3ATA).

 

[MBH]

IMHO there are no benefits. (I assume you are saying that nitrox is less narcotic than air? I dont buy that )

Yes that's exactly what I said.
Nitrogen is known to have narcotic effects.
That's why it's called "nitrogen narcosis".

 

[Twiddles]

MBH read the link in Nitrox the wonder gas post, there is virtually no reduction in risk of narcosis by using Nitrox, at least according to Dr. Bennet from DAN.

 

[boulderjohn]

There are now over 9 million certified divers. Most of whom are classified as recreational divers, who dive with only an OW card, who dive on vacation only etc, etc, etc. Who do not hit NDL but rather suck the tank dry like a Kirby on a throwrug.

I am so sorry that your dive experience must have been with so many divers such as you describe. In my own experience, it is not at all rare to find people who find a benefit on single dives, let alone multiple dives, where it really pays off.

I just flipped open own log book and looked at the first nitrox dive I saw. Site = Babylon, on the island of Saba. Maximum depth 89 feet on EAN 32. Average depth for the dive was 49 feet (counts everything, including the safety stop). Total time = 55 minutes. Tank = Aluminum 80.

The real benefit was that I was following an earlier dive to Shark Shoals on Saba (1:46 SI), with a maximum depth of 128 feet on EAN 30. My average depth was 75 feet, for a total bottom time of 31 minutes. I had more than 1,000 pounds in my aluminum tank when we surfaced. If I were not using nitrox, I would have had to surace way, way sooner.

I am no superman. Lots of people--especially slightly build ladies--can do better than that. I weigh about 200 pounds, so I use a lot more air than smaller people.

I don't see why you seem to think what is really average diving = being a superman.

 

[ianr33]

Yes that's exactly what I said.
Nitrogen is known to have narcotic effects.
That's why it's called "nitrogen narcosis".

But oxygen is more soluble in lipids than is nitrogen,so should be MORE narcotic than nitrogen.

Next question............

 

[boulderjohn]

Yes that's exactly what I said.
Nitrogen is known to have narcotic effects.
That's why it's called "nitrogen narcosis".

Unfortunately, many gases, including oxygen, have that narcotic effect. That is why nitrox has no real benefit for narcosis.

Helium has much less of a narcotic effect, which is why it is used by tech divers to reduce narcosis.

 

[grf88]

For the same dive profile Nitrox will result in lower nitrogen loading. I don't think that anybody has ever suggested that nitrogen loading is a good thing so even if you do not use it to extend the dive it can have benefits. If you increase the length of the dive by only 50% of the additional time that Nitrox provides you have still reduced you nitrogen loading and extended your dive. Obviously you need adequate gas for the dive but there are plenty of options other than Al80's and doubles.

 

[adurso]

There are now over 9 million certified divers. Most of whom are classified as recreational divers, who dive with only an OW card, who dive on vacation only etc, etc, etc. Who do not hit NDL but rather suck the tank dry like a Kirby on a throwrug.

Adurso Im glad you asked =),

Step 1- OOA Regulator Exchange & Problem Assessment at Depth
time at depth (in minutes) X depth (ata) X RMV of 2 divers (working RMV) =

Step 2- Ascent from Depth to 1 Stop
time to ascend (in minutes) X avg depth (max depth to stop depth, in ata) X RMV =
Step 3- *Stop (1 minute deep stop or 3 minute safety stop)
stop time X stop depth (ata) X RMV =

Step 4- *Ascent from 1 Stop to Safety Stop (max depth deeper than 80fsw)
time to ascend X avg depth (stop depth to safety stop depth) X RMV =
Step 5- Safety Stop
time at stop X stop depth (ata) X RMV =
Step 6- Ascent from Safety Stop
time to ascend X avg depth (stop depth to surface, ata) X RMV =

Step 7- Total Gas Used
Add steps 1-6

Step 8- Convert to PSI
CuFt of gas needed / rated volume of tank / rated pressure of tank =
Step 9- Add 200psi for Reserve

Add 200 to step 8 for total Rock Bottom

Punch in 70' see how well you do, keeping in mind your breathing at 70' for 35 minutes (3ATA).

I know how well I do. I am guessing that you find based upon our calculations that the majority of divers will not? Bearing in mind that the staggering numbers of divers you mention have no idea what rock bottom is and could not care less? I think many divers are taught to surface with no less than 500/700 psi. Acquaintances in the business complain about their rental tanks being returned quite dry...

So because many cannot dive at 70 over 35 min then one can?

 

[Stu S.]

Boynton Beach Florida has reefs right around 65 feet. You can have dive number 1 for 63 minutes, a surface interval of 42 minutes, and then dive for an hour again. This is right out of my logbook. I used EAN 34 and a Cressi Computer.

That's why most divers use nitrox at this location.

Check the air tables and see how long a surface interval is required after dive 1. I believe it is 24 hours.

 

[Twiddles]

Boulderjohn, you are an instructor which places you in what the top 10% (lets be real conservative as that would indicate 900,000 instructors). You also stand to gain by training recreational divers in the use of Nitrox regardless of its benefit. Can you honestly say that MOST divers would gain anything from Nitrox? Not divers you know, or dive with, but most recreational divers.

No Adurso as my earlier posts stated, because you can does not mean the majority would, could or should. The ascent alone burns more than half your air (and since your ascending your using less than you would at 70').