Common reasons for diving nitrox

[Quero]

The one hour rule was definitely in the PADI Nitrox class when I took it. Not that I've ever seen anyone worry about following it.

Perhaps you are thinking of the recommendation regarding oxygen exposure? That advice is in the nature of a loose guideline rather than a rule per se, and mainly applies if the diver's allowable exposure reaches 50%. The NOAA O2 exposure limits as adopted by PADI actually don't give any surface interval credit but rather just add all the exposure percentages up dive by dive over a 24-hour span. Regardless of the lack of SI credit, offgassing obviously does take place during surface intervals, and the longer those are, the more both the residual nitrogen and oxygen will dissipate, which can only be good for the diver. It's true that most recreational divers don't pay much attention to the oxygen exposure surface interval recommendation, probably because at recreational limits (in particular the MOD limits and no-deco diving limits), elevated percentages of O2 exposure are highly unusual.

 

[TheRedHead]

I use the EAD to calculate SI with recreational nitrox. But I'm not PADI trained.

 

[Dave in PA]

I wanted to vote for all four reasons:
1) Obviously, especially under 60' depths. Sometimes I do 4-5 dives in a day (fun dives and class dives)
2) This really helps on the 4-5 dives day. A SI between 45-60 min will keep me going all day with nitrox
3) I can feel the effects below 90 feet on air, I feel much more clear headed on nitrox to the same depths.
4) Some people say BS to this one, but all I know is if I am diving nitrox, I can go home after a day of diving, cut the grass and take my better half out for dinner and a movie. After a couple of air dives, I am ready for a nap.

your mileage may vary.

 

[jtivat]

The one hour rule was definitely in the PADI Nitrox class when I took it. Not that I've ever seen anyone worry about following it.

I just re-read the PADI Enriched Air Diver manual and it says nothing about a one hour minimum SI however all of the examples do use a one or two hour SI.

 

[Jon C]

i use nitrox because

it makes me smarter
it makes chicks dig me
it fights acne
it doesn't give me a hangover
it can be used as paint thinner
good for degreasing engines!
goes better with coke!

and... most of all

because love may come and love may go, but a Nitrox dive goes on and on

Why H2Andy...You're a romantic! Who could've known!

 

[BarryNL]

I just re-read the PADI Enriched Air Diver manual and it says nothing about a one hour minimum SI however all of the examples do use a one or two hour SI.

There is a very good reason for having a one hour interval, which is that the brain and spinal tissues are "medium" tissues and usually modelled with a 12.5 minute half-time, which means that after a 1 hour interval these tissues are about 96% off-gassed. Considering these tissues cause some of the biggest problems if "bent" then off-gassing them almost completely between dives is a good idea.

It has nothing to do with nitrox though...

More info: http://www.diversalertnetwork.org/news/article.asp?newsid=514

 

[Tienuts]

I am an EANx instructor, and it's mostly what I teach. I can tell you with absoulute certianty, that Nitrox does not make you less tired. Blind studies have proven that.

What usually makes you fatigued after a dive, is the ascent rate you use when you are ending your dive. A slow ascent rate, (30 ft per min) with multiple stops (i.e. 70 ft stop 1 min, 50 ft stop 1 min, 15 ft stop 3-5 min) will make you less tired.

As far as other things mentioned here:

- If diving nitrox using nitrox tables, it is not any safer.
- Oxygen is NOT narcotic, it is quite the opposit, a Central Nervous System stimulant
- It does not lower narcosis (the onset of narcosis is from 100-130 ft, just where the MOD's of nitrox start)
- Nitrox does not make you breathe less

It does one thing. It extends your bottom time. (And aids in decompression if you are on deco dives)

Anyone who does not beleive me, please take my class and I will show you otherwise.

 

[BarryNL]

Every dive shop in the world has EANx21. It's called compressed air.

Strictly speaking, the EAN stands for Enriched Air Nitrox which only applies to mixes which are enriched with extra oxygen, so 21% nitrox is not an EANx mix.

 

[BarryNL]

I am an EANx instructor, and it's mostly what I teach. I can tell you with absoulute certianty, that Nitrox does not make you less tired. Blind studies have proven that.

What usually makes you fatigued after a dive, is the ascent rate you use when you are ending your dive. A slow ascent rate, (30 ft per min) with multiple stops (i.e. 70 ft stop 1 min, 50 ft stop 1 min, 15 ft stop 3-5 min) will make you less tired.

In other words, sub-clinical bends make you tired. Nitrox means less N2 take up and thus lower incidence of sub-clinical bends - hence nitrox makes you less tired (if you regularly practice poor ascents). I'm aware of the blind studies but they were done in deco chambers with ideal ascent profiles so would not cause sub-clinical bends.

- Oxygen is NOT narcotic, it is quite the opposit, a Central Nervous System stimulant

Cocaine, amphetamines and MDMA are not narcotics but are regularly referred to as such. The term is a bit confusing but tends to be used more to (incorrectly) mean any mood altering substance. O2 is narcotic in the sense that it affects you ability to think clearly just as much as N2 does.

- It does not lower narcosis (the onset of narcosis is from 100-130 ft, just where the MOD's of nitrox start)

Narcosis starts from 1m - it's just not generally noticable until 20m or so and, for most people, not problematic until deeper.

 

[H2Andy]

Why H2Andy...You're a romantic! Who could've known!

yeah well, it's a well kept secret

REALLY well kept