Nitrox

[hroark2112]

That's what the class is for...to teach you how to figure out these things.

It will depend on the mix.

 

[swimmer_spe]

That's what the class is for...to teach you how to figure out these things.

It will depend on the mix.

I hate those answers.

I know how to figure it out for air. I do not know how to figure it out in Nitrox. I know there are many different types of mixes. I do not know the types though, so, pick a common one, and go with it.

I am not exact information, I am looking for a general comparison.

 

[boulderjohn]

No. I am considering it, if it will give me more time in the water at depth.

Why should I get another certification if it will not matter.

Can someone do a comparison between air and nitrox? Do it for 6 dives, max depth of 80 feet, with SI of 1 hour, starting diving at the same time every morning.

How much more in water, at depth time would I get?

I am really not sure what you mean--6 dives in a day for multiple days? You are really asking a lot. This is especially true because you will likely not be doing square profiles, especially in Australia.

Let me give you at least a little of a comparison for a 3 dive day using PADI tables.

1. First dive of the day to 80 feet. For Diver A on air, the maximum time allowed is 30 minutes. Let's say he does 25. Diver B is on nitrox 32. His maximum allowed time is 45 minutes, and he does 35.

2. The second dive of the day will be to 70 feet. Diver A has been out of the water for 1:10, and Diver B has been out for 1:00. Diver A now has a maximum bottom time time of 28. Lets say he does 23. Diver B has a maximum bottom time of 41 minutes. Let's say he does 35.

3. The third dive of the day will be to 60 feet. Diver A has been out of the water for 1:12, and Diver B has been out for 1:00. Diver A now has a maximum bottom time time of 39. Lets say he does it all. Diver B has a maximum bottom time of 60 minutes. Let's say he does it all.

Totals: Diver A on air: 92 minutes of bottom time. Diver B on nitrox 32: 132 minutes of bottom time--40 more minutes, which is longer than any of Diver A's dives. It is like he got an extra dive.

(I went through the tables quickly--let me know if I made any errors.)

 

[Basking Ridge Diver]

I am really not sure what you mean--6 dives in a day for multiple days? You are really asking a lot. This is especially true because you will likely not be doing square profiles, especially in Australia.

Let me give you at least a little of a comparison for a 3 dive day using PADI tables.

1. First dive of the day to 80 feet. For Diver A on air, the maximum time allowed is 30 minutes. Let's say he does 25. Diver B is on nitrox 32. His maximum allowed time is 45 minutes, and he does 35.

2. The second dive of the day will be to 70 feet. Diver A has been out of the water for 1:10, and Diver B has been out for 1:00. Diver A now has a maximum bottom time time of 28. Lets say he does 23. Diver B has a maximum bottom time of 41 minutes. Let's say he does 35.

3. The third dive of the day will be to 60 feet. Diver A has been out of the water for 1:12, and Diver B has been out for 1:00. Diver A now has a maximum bottom time time of 39. Lets say he does it all. Diver B has a maximum bottom time of 60 minutes. Let's say he does it all.

Totals: Diver A on air: 92 minutes of bottom time. Diver B on nitrox 32: 132 minutes of bottom time--40 more minutes, which is longer than any of Diver A's dives. It is like he got an extra dive.

(I went through the tables quickly--let me know if I made any errors.)

I cant tell if you made any errors - my comment would be it depends on the volume of your tank(s) - most - not all of us that use air - use AL80s. So I am not sure that at 60 feet at one hour for me is realistic - so in getting that bottom time - you would then need to upgrade your tank(s) to get the full benefit of Nitrox - correct?

 

[swimmer_spe]

I am really not sure what you mean--6 dives in a day for multiple days? You are really asking a lot. This is especially true because you will likely not be doing square profiles, especially in Australia.

Let me give you at least a little of a comparison for a 3 dive day using PADI tables.

1. First dive of the day to 80 feet. For Diver A on air, the maximum time allowed is 30 minutes. Let's say he does 25. Diver B is on nitrox 32. His maximum allowed time is 45 minutes, and he does 35.

2. The second dive of the day will be to 70 feet. Diver A has been out of the water for 1:10, and Diver B has been out for 1:00. Diver A now has a maximum bottom time time of 28. Lets say he does 23. Diver B has a maximum bottom time of 41 minutes. Let's say he does 35.

3. The third dive of the day will be to 60 feet. Diver A has been out of the water for 1:12, and Diver B has been out for 1:00. Diver A now has a maximum bottom time time of 39. Lets say he does it all. Diver B has a maximum bottom time of 60 minutes. Let's say he does it all.

Totals: Diver A on air: 92 minutes of bottom time. Diver B on nitrox 32: 132 minutes of bottom time--40 more minutes, which is longer than any of Diver A's dives. It is like he got an extra dive.

(I went through the tables quickly--let me know if I made any errors.)

That helps me understand just how much more it is worth getting the certification.

For the cost and time of a course, to get that much time out of just 3 dives would be amazing. I know I would last a tank in warm waters, so, as long as I can maximize the gas, it would be better to go Nitrox.

 

[Brandon]

How much more in water, at depth time would I get?

I think I'd rather answer your original question re: how many dives are done in a day, and not whether or not nitrox is worth it.

My buddy and I did Spoilsport in 2010 and did all 25 dives offered during the 7 day trip. Bottom times were 50-60+ minutes on all dives, and honestly... you'd be hard pressed to do more than that; NDL and gas consumption notwithstanding.

If you haven't dove like that before - it's a lot of diving in a short time period. Here's a rough example:

0630 - Wakey wakey.
0645 - Quick snack breakfast.
0700 - First dive briefing
0715-0830 - First dive
0830 - Proper breakfast
1000 - Second dive briefing
1015-1130 - Second Dive
1130-1230 - Lunch / transit to new dive site.
1300 - Third dive briefing
1315-1430 - Third Dive
1445- 1545 - SI
1600 - 1700 - Fourth Dive
1730 - Dinner

We ended a lot of dives well ahead of our gas/deco plan (average depth is shallow on typical GBR liveaboard sites) - because the schedule demanded it. Dive for more than an hour, and you might miss the window for a second dive. You might even miss a meal(!!!).

We dove below the rest of the groups for the first couple of dives thinking we'd see cooler critters, and it was pointless. Except for a few sites, the vast majority of the good stuff on the GBR is 60' or shallower. We listened carefully to the briefings and self-guided on all of the sites, and most of our dives ended up with an average depth of 35-45' and max depths around 80 feet. This trip was also followed by another 2 weeks and 35 dives in PNG, where we did the same thing with slightly deeper profiles.

For us - we dive everything <100' on 32% anyway, so nitrox for this trip was more a foregone conclusion rather than a consideration. If I had to give a reason, I'd cite the increased safety margins when diving multiple dives per day over an extended period, or the increased safety margins nitrox brings to recreational profiles (as long as you respect the MOD).

 

[boulderjohn]

I cant tell if you made any errors - my comment would be it depends on the volume of your tank(s) - most - not all of us that use air - use AL80s. So I am not sure that at 60 feet at one hour for me is realistic - so in getting that bottom time - you would then need to upgrade your tank(s) to get the full benefit of Nitrox - correct?

If you do not have the breathing capacity to do 60 minutes at 60 feet, you would need larger tanks--that is correct. Or you could cut off a few minutes.

I just put out one set of numbers for one kind of dives. There are a lot of variables to be considered. When we did the dives in Australia, the air divers were getting pretty much the same length dives we were. But I bet we were spending more time at greater depth. So what? Maybe the divers were better shallower. In contrast, in the liveaboard dives I did in Thailand, Truk Lagoon and in the Galapagos, there was little so see shallow, and the air divers (few that there were) were at an obviously significant disadvantage. There are a lot of factors to consider.

 

[Oldbear]

I hate to be the scuba police, BUT...
Nitrox will either
- extend your bottom time
OR
- reduce your need to push the NDL limits.
It can not do both at the same time. Choose 1 or the other. They are mutually exclusive. There is no free lunch.

While your state is not 100% false, I do not believe it to be 100% correct either. I think it depends where on the perspective NDL line you set your bottom time at.

I find that "Extend Your Bottom Time" and "Reduce Your Need to Push the NDL Limits" can both be achieved:

Air (21% O2) 20 meter dive has a NDL of 45 Minutes
EANx32 (32% O2) 20 meter dive has a NDL of 75 minutes
EANx36 (36% o2) 20 meter dive has a NDL of 95 minutes

If I dive EAN 32 instead of with air (21% O2) at 20 meters for 60 minutes didn't I just "extend my bottom time" by 15 minutes (60 minutes bottom time - 45 minutes NDL of Air) and still had 15 minutes of NDL in reserve (75 minutes NDL 32% O2 - 60 minutes of bottom time), thus not pushing my NDL?

 

[KeithG]

While your state is not 100% false, I do not believe it to be 100% correct either. I think it depends where on the perspective NDL line you set your bottom time at.

I find that "Extend Your Bottom Time" and "Reduce Your Need to Push the NDL Limits" can both be achieved:

Air (21% O2) 20 meter dive has a NDL of 45 Minutes
EANx32 (32% O2) 20 meter dive has a NDL of 75 minutes
EANx36 (36% o2) 20 meter dive has a NDL of 95 minutes

If I dive EAN 32 instead of with air (21% O2) at 20 meters for 60 minutes didn't I just "extend my bottom time" by 15 minutes (60 minutes bottom time - 45 minutes NDL of Air) and still had 15 minutes of NDL in reserve (75 minutes NDL 32% O2 - 60 minutes of bottom time), thus not pushing my NDL?

agreed. it can be done, but in my live aboard experience it very seldom works out this way. humans often behave strangely.

the dive boat keeps to a schedule and hence limits bottom time (either 60 or 70 minutes). the nitrox divers are paying extra for ean32 for which they want to get their moneys worth. this generally means they go deeper for longer and then run up against NDLs quickly. generally there are very few divers that max out their bottom time. that does not seem to be a goal.

this behaviour may also be (more?) related to many divers being dive computer jockeys with little to no ability to pre plan a series of dive profiles.

 

[swimmer_spe]

agreed. it can be done, but in my live aboard experience it very seldom works out this way. humans often behave strangely.

the dive boat keeps to a schedule and hence limits bottom time (either 60 or 70 minutes). the nitrox divers are paying extra for ean32 for which they want to get their moneys worth. this generally means they go deeper for longer and then run up against NDLs quickly. generally there are very few divers that max out their bottom time. that does not seem to be a goal.

this behaviour may also be (more?) related to many divers being dive computer jockeys with little to no ability to pre plan a series of dive profiles.

So, are you actually saying that regardless of nitrox or not, I will not hit my NDL?

So, in the situation described, what benefits do I get?