Brand new to nitrox

[Just phil]

Hi all,

I've been diving for a few years but am new to nitrox.
I completed the nitrox course & wanted to ask the real world brain trust found here.

Couple of silly questions maybe, but here goes:

All using nitrox changes is the amount of gas loading up in my body, right?
It doesn't enable me to stay down longer or anything, right?
It does allow me to dive more frequently in a given period of time, right?

I ask because my wife is taking me to Bonaire for my birthday...

Thanx in advance,
Phil

 

[Lake Hickory Scuba]

Hopefully these will help you out.

Nitrox is a Myth



Advantages of Nitrox

 

[Steve_C]

Hi all,
It doesn't enable me to stay down longer or anything, right?

Simple answer:

Are your dives NDL limited or Air limited? If your dives are air limited, then the Nitrox will not help. If however your dives (both or either) are NDL limited then Nitrox will give you more NDL and those allow longer dives.

If your dives are NDL limited and are deep then you may have to start using lighter mixes. (Actual deep not greater than 60 ft deep)

 

[Johnoly]

I completed the nitrox course...

What shop/Op did you complete the course with?

 

[mi000ke]

If you want to get adventurous, you can compute the impact of using nitrox if you know your SAC and dive profile. In general you have to have a pretty good SAC and be diving near MOD for a while to make a difference.

Example:

(Results from Dive Planner app set to PADI specs and assuming EAN32, and while approximate and "theoretical", I think they make the point - and I think/hope the math is basically correct):

Say, your SAC rate is .7 cf/min
And your time-weighted average depth for the dive you plan to do is 66' (3 ATM)
Then your average consumption will be 3 x .7 = 2.1 cf/min
For a 77 cf tank, you will have about 37 minutes of air (not including 500 psi safety buffer)
Your NDL will be about 40 min for air, and about 55 for nitrox, but it won't make a difference as you will run out of gas before you hit either NDL, and even soon if you set aside a safety reserve of gas.

At 50' average (2.5 ATM) your air will last 44 minutes ( or less with safety reserve) but your air NDL is 80 and nitrox is 140 and again you are gas-constrained. At 33' average your NDL is even greater than your air limits.

Going deeper, at 99' average (4 ATM) your air will last about 28 minutes (again, less with safety reserve) . Your air ndl is 20 min and your nitrox ndl is 30 minutes - so... you will gain all of 8 minutes if you push it to the limit, and probably no gain if you include safety reserve. Instead of only 20 min based on your air NDL, you can go all the way to your gas limit of 28 and still be under the nitrox NDL. But you'd have to be spending a lot of time near your MOD to get that benefit, and hope you can get back to the surface just as your air runs out.

Now, for me, I have a SAC of about .4 so when I do a dive at an average depth of 50', I have theoretically over 75 minutes of air in my tank. And I almost always get over an hour on a 60' reef dive with 500-700 psi to spare. But even then I'm still not reaching either air or nitrox NDL.

HOWEVER ... if you do multiple dives (or if you are tired old fart like me) then nitrox may make sense. And you can go through this same exercise above for multiple dives, adjusting your ndl for the previous dive and surface interval. I have hit my NDL on subsequent dives when on air enough that I use nitrox primarily for that reason (especially with dive ops that want to get you back in the water fast so they can get the next group on board).

 

[uncfnp]

Hi all,

I've been diving for a few years but am new to nitrox.
I completed the nitrox course & wanted to ask the real world brain trust found here.

Couple of silly questions maybe, but here goes:

All using nitrox changes is the amount of gas loading up in my body, right?
It doesn't enable me to stay down longer or anything, right?
It does allow me to dive more frequently in a given period of time, right?

I ask because my wife is taking me to Bonaire for my birthday...

Thanx in advance,
Phil

Congrats on Bonaire!

Yes the purpose of nitrox is to lessen the amount of nitrogen loading for the same time and depth on air. So yes, you will have more bottom time on nitrox, as long as you still have gas. Or longer repetitive dives.

Or you can use it as an added safety margin by diving the same profile times as air so you will end your dives with less nitrogen load.

 

[cneal]

On Bonaire it is easy to do four or five dives a day if you want. On the fourth and fifth dives of the day the bottom time will be noticably increased using nitrox.

 

[drrich2]

In practical real world use, I've seen nitrox come in handy for 2 main scenarios; high frequency diving (e.g.: 5/day on a live-aboard or Bonaire), or diving where much of the dive is quite deep (e.g.: off-shore wreck diving out of North Carolina, or drifting along deep ledges out of Jupiter, FL).

Richard.

 

[TrimixToo]

Hi all,

I've been diving for a few years but am new to nitrox.
I completed the nitrox course & wanted to ask the real world brain trust found here.

Couple of silly questions maybe, but here goes:

All using nitrox changes is the amount of gas loading up in my body, right?
It doesn't enable me to stay down longer or anything, right?
It does allow me to dive more frequently in a given period of time, right?

I ask because my wife is taking me to Bonaire for my birthday...

Thanx in advance,
Phil

You will love Bonaire. Enjoy it!

However, if you completed a Nitrox course and cannot answer these questions, I have to observe that the course was not terribly effective in teaching you what you need to know. You should have a discussion about this with the instructor who signed you off as certified to use it about these questions, and also about testing, MODs, and O2 exposure limits if you do not understand them thoroughly. It is important not to simply trust other people you dive (including DMs) to tell you what the safe limits are for Nitrox on a particular day.

(Others have answered your questions above, I think.)

 

[DiverDownD3]

What shop/Op did you complete the course with?

This is a good question. The questions the OP asked should have been covered in the class