To nitrox or not to nitrox

I'm a novice diver in the south of Ireland, currently half way through my
AOWD. I've done some reading on nitrox and I do think that sooner or later I
will start using nitrox ... probably sooner rather than later.

I'm nearly finished with my gear research and set to buy pretty soon. I am
however confused by regulators that carry the word nitrox in their model
name. What's the story with nitrox regs? Are they REQUIRED for nitrox diving
or are they only more SUITABLE than air regs, e.g. regarding pressure
levels.
Assuming that I will take a mixed air course next year, should I be
considering this in my gear purchase? Can a nitrox "enabled" reg be used for
normal air as well?

I'm somewhat confused about this. Please enlighten me.

Cheers,

Marcus

In article <bjfgpg$r96$1@kermit.esat.net>, Marcus Viertel
<mviertel@bluebottle.com> wrote:

€I'm a novice diver in the south of Ireland, currently half way through my
€AOWD. I've done some reading on nitrox and I do think that sooner or later I
€will start using nitrox ... probably sooner rather than later.
€
€I'm nearly finished with my gear research and set to buy pretty soon. I am
€however confused by regulators that carry the word nitrox in their model
€name. What's the story with nitrox regs? Are they REQUIRED for nitrox diving
€or are they only more SUITABLE than air regs, e.g. regarding pressure
€levels.
€Assuming that I will take a mixed air course next year, should I be
€considering this in my gear purchase? Can a nitrox "enabled" reg be used for
€normal air as well?
€
€I'm somewhat confused about this. Please enlighten me.
€
€

Almost without exception, any regulator presently on the market can be
used with enriched air mixtures up to 40%.

Above 40% (and this is really a somewhat arbitrary cut off point), the
regulator should be both "O2 clean" and rated for pure oxygen service.
It's not that 41% is such a dangerous number, but mixtures above 40%
are typically used as deco gasses, which are much higher than 40%. 50%
is a common gas for the 70 fsw switch, and either 80/20 or 100% O2 are
typically used from 20 fsw and upwards. In general, deco regs should be
rated for pure O2 service, even if used on 50/50, because you tend to
switch deco regs around a lot to different gas bottles, and it just
makes sense to have them all be O2 rated. Regs used for high oxygen
concentrations use O2 compatible lubricants (which is actually not a
big deal, because the same lubricant is used for non-O2 clean products
nowadays), and O2 compatible elastomers. There is usually a slight
*decrease* in reg performance between a "standard" reg and one that has
been converted for pure O2 use. Since these are used primarily during
decompression, performance isn't that big of an issue.

Regs used for recreational nitrox, 40% and below, can be freely
switched between air and nitrox mixtures. Using an O2 clean reg on
plain air *could* contaminate the reg and render it "O2 unclean" if the
plain air was dirty enough.

Alan

alan@nonono_irsi.com stopped playing nethack just long enough to say:
>
>Almost without exception, any regulator presently on the market can be
>used with enriched air mixtures up to 40%.

True - although some manufacturers will not warrant their equipment for
use with Nitrox. That's something to consider if warranty support is an
important issue to you.

>Above 40% (and this is really a somewhat arbitrary cut off point),

It's not arbitrary at all. The "40% rule" comes from tests that were
conducted by NASA in the 1960s, in which they determined that gas
mixtures containing more than 40% oxygen were roughly equivalent to
pure oxygen in terms of their ability to contribute to combustion.

-JimG

--
Jim Greenlee (jkg@cc.gatech.edu) My parents visited a planet where the
College of Computing native life had no bilateral symmetry,
Georgia Tech, Atlanta, GA 30332 and all I got was this lousy F-shirt

"Marcus Viertel" <mviertel@bluebottle.com> wrote in message
news:bjfgpg$r96$1@kermit.esat.net...
> I'm a novice diver in the south of Ireland, currently half way through my
> AOWD. I've done some reading on nitrox and I do think that sooner or later
I
> will start using nitrox ... probably sooner rather than later.

If you continue to dive, I think so too.

> I'm nearly finished with my gear research and set to buy pretty soon. I am
> however confused by regulators that carry the word nitrox in their model
> name. What's the story with nitrox regs? Are they REQUIRED for nitrox
diving
> or are they only more SUITABLE than air regs, e.g. regarding pressure
> levels.

Neither. Almost all modern regulators are suitable for nitrox use. You
don't run into problems until the percentage of Oxygen gets higher than any
nitrox diver is likely to use. The high O2 mixes are normally reserved for
accelerated decompression. Before you get there, you'll own more than one
additional regulator and will be in a better position to decide which one
you like for yourself. Unless the regulator specifically says "not to be
used with nitox," don't worry about it. Do, however, consider how cold the
water you'll dive in is. Not all regulators are created equal in this
respect.

> Assuming that I will take a mixed air course next year, should I be
considering this in my gear purchase? Can a nitrox "enabled" reg be used for
> normal air as well?

Watch your terminology. Mix often implies trimix, i.e. an oxygen, nitrogen,
helium mix. Nitrox or EAN normally means a mix of air and oxygen. Nitrox
courses normally certify you up to 40% oxygen. If this is the highest level
of oxygen you use, you can use the same regulator for all of your diving.
If you're going to use much higher oxygen levels, you probably should
dedicate a regulator for that use to avoid contaminants that might ignite in
a very high oxygen environment.

Lee

Jim.Greenlee@cc.gatech.edu left this mess on Sun, 7 Sep 2003 17:40:59 +0000
(UTC) for The Way to clean up:
>
>alan@nonono_irsi.com stopped playing nethack just long enough to say:
>>
>>Almost without exception, any regulator presently on the market can be
>>used with enriched air mixtures up to 40%.
>
>True - although some manufacturers will not warrant their equipment for
>use with Nitrox. That's something to consider if warranty support is an
>important issue to you.
>
>>Above 40% (and this is really a somewhat arbitrary cut off point),
>
>It's not arbitrary at all. The "40% rule" comes from tests that were
>conducted by NASA in the 1960s, in which they determined that gas
>mixtures containing more than 40% oxygen were roughly equivalent to
>pure oxygen in terms of their ability to contribute to combustion.
>

Was that the study done in response to the Apollo 1 tragedy?

Tao te Carl

"It takes a village to have an idiot." - Carl (c) 2003

Jim.Greenlee@cc.gatech.edu wrote:

> alan@nonono_irsi.com stopped playing nethack just long enough to say:
> >
> >Almost without exception, any regulator presently on the market can be
> >used with enriched air mixtures up to 40%.
>
> True - although some manufacturers will not warrant their equipment for
> use with Nitrox. That's something to consider if warranty support is an
> important issue to you.


The manufacturer warranty issue for mixes between 21-40% has been
considered by some/many to be little more than a means to an end excuse
for them to justify the consumer paying extra for a 'Nitrox certified'
kit.

And when it comes to the question of someone violating a warranty with a
32% mix, is there really any way for the manufacturer to prove it?


-hh

H. Huntzinger left this mess on Tue, 09 Sep 2003 07:31:23 -0400 for The Way to
clean up:
>
>Jim.Greenlee@cc.gatech.edu wrote:
>
>> alan@nonono_irsi.com stopped playing nethack just long enough to say:
>> >
>> >Almost without exception, any regulator presently on the market can be
>> >used with enriched air mixtures up to 40%.
>>
>> True - although some manufacturers will not warrant their equipment for
>> use with Nitrox. That's something to consider if warranty support is an
>> important issue to you.
>
>
>The manufacturer warranty issue for mixes between 21-40% has been
>considered by some/many to be little more than a means to an end excuse
>for them to justify the consumer paying extra for a 'Nitrox certified'
>kit.
>
>And when it comes to the question of someone violating a warranty with a
>32% mix, is there really any way for the manufacturer to prove it?
>

An innocent diver might log the dive as an EANx dive. If I was defending a
company, that's the first place I'd look. Then maybe check out his LDS, if he
doesn't log.

Tao te Carl

"It takes a village to have an idiot." - Carl (c) 2003