Diving Nitrox -- pros & cons

large_diver · Jul 24, 2003

I have been diving strictly air up to this point and am considering the conversion to Nitrox.

Most of my diving is in the 20-80 foot, range, with occasional dives to 100 ft (nothing deeper than 100).

The pros & cons of using Nitrox as I see them are as follows:

Pros:
- Physical benefits -- reduced nitrogen levels
- Decreased gas density = decreased breathing effort
- Additonal protection against DCS (asuming following air NDLs)
- Additional bottom time (assuming following Nitrox NDLs)
- Potential increase in breathing capacity at depth vs. air

Cons:
- Oxtox risk
- More expensive
- Complexity -- need to analyze breathing gas carefully before using

Also, I have mild allergen-induced asthma -- not sure if there are any issues regarding Nitrox and asthma.

Any feedback is greatly appreciated -- thanks.

Green_Manelishi · Jul 24, 2003

Don't forget you'll need to own "extra" tanks that will not be
used for "standard" air fills. You really don't want to have to
clean the tanks every time you plan on using EAN.

I'd recommend using "clean" air in your tanks at all times.
Clean the tanks that you do own and then avoid "dirtying them" with a regular air fill.

And just say "NO" to big stickers !!!

Big-t-2538 · Jul 24, 2003

Nitrox is good for all the reasons you mentioned, and staying within the depths you mention, you are at a very very low risk of an ox-tox.

Analyzing gas is not as complicated as it sounds, and you can buy kits and build your own analyzer for around 150$ for a "second opinion"

As for allergen asthma, I beleive the EANx would be better b/c there have to be les contaminates in the tank before you even get a fill, so this would probably be another "pro", but I'm not a medical dude, so I can't say for sure.

Lastly, you do NOT need new tanks or extras...just get the ones you have O2 cleaned, get the oxyhacker's manual as a great reference tool for anything related to O2. You will need to be picky about what kind of air fills you get (if you get air fills again)...the air has to be "hyperfiltered" air...or the equivalent of EANx 21...essentially the air has been cleaned so there are less contaminates in it.

Green_Manelishi · Jul 24, 2003

Big-t ...

Poorly worded on my part. I agree that L_D will not need
extra tanks IF he keeps the tanks he has clean.

My tanks are clean and stay that way by using 'hyperfiltered'
air when I dive air.

notabob · Jul 24, 2003

Actually, you should find out what type of Nitrox fill method your LDS uses before you plunge the $$ on O2 cleaning. Most LDSs in Massachusetts bank EAN40 or less and will make a custom mix based on that. With the O2 percentage below 40%, O2 cleaning is not needed, and you can alternate air and EANx fills as you wish on the same set of tanks.

If, however, your LDS fills via partial pressure method utilizing O2 or EANx of higher than 40%, then O2 cleaning and hyperfiltered air fills will certainly be in order.

-Roman.

Big-t-2538 · Jul 24, 2003

while I agree with notabob about the LDS...the only thing is if you are somewhere and they fill EANx there are not many people that continuous blend or bank EANx 40 and top off with air....

So if you are somewhere else, a lot of people PP fill, so you might as well bite the bullet now, and just get them cleaned....besides then you'll have 1 less thing to worry about.

However, if you don't travel, this is quite possibly a non-issue.

Charlie99 · Jul 24, 2003

large_diver once bubbled...
as I see them are as follows:

Pros:
- Decreased gas density = decreased breathing effort

You are probably thinking of trimix with significant percentages of Helium. Trimix does have decreased breathing effort compared to air or EAN.

O2 and N2 are pretty close in density(and O2 denser anyway) so you won't notice the theoretically harder breathing of nitrox.

large_diver · Jul 24, 2003

First -- thanks for all the prompt responses. G_M -- long time no see.

I am pretty much in the dark when it comes to Nitrox...so a few questions...

Roman -- when you say that they bank EAN40....I assume the filling method is that they partially fill your tanks with the EAN40 and then add air to get to the O2% you want -- correct?

Big-T....when you say "alot of people PP fill".....are you are talking about adding 100% O2 and then adding air.....?

All -- please explain the following (1) why the need for O2 cleaning at higher 02 %s and not at lower %s; and (2) the % when O2 cleaning is required.

Charlie -- it may be that I mis-remembered this. Can anyone else confirm the differences between air and Nitrox in terms of breathing effort and breathing capacity?

Thanks.

notabob · Jul 24, 2003

They'll measure the contents of the tank (PSI and O2 fraction), then calculate how much EAN40 (or 36, or whatever they got) and air needs to be added in order to get you to your desired O2 % at fill pressure.

O2 cleaning is required if you will be introducing gases with O2 % higher than 40%. At these elevated levels, oxygen can potentially combust spontaneously when combined with hydrocarbon contaminants in your tanks and valves. O2 cleaning removes the contaminants from the inside of your tanks and valves, and replaces valve o-rings with those that are suitable for use with elevated O2 levels (i.e. viton o-rings)

-Roman.

BigJetDriver · Jul 25, 2003

notabob once bubbled...
...O2 cleaning is required if you will be introducing gases with O2 % higher than 40%. At these elevated levels, oxygen can potentially combust spontaneously when combined with hydrocarbon contaminants in your tanks and valves. O2 cleaning removes the contaminants from the inside of your tanks and valves, and replaces valve o-rings with those that are suitable for use with elevated O2 levels (i.e. viton o-rings)

-Roman.

A minor correction if I may. It is not the oxygen that will spontaneously combust. What happens is that, in the presence of so much available oxidizer, the required ignition temperature of a whole lot of materials, such as ordinary o-rings, or ordinary lubricants, is much lower than normal. It can get so low that adiabatic compression and molecular friction will be enough to reach ignition temperature.

The rest is quite correct, and a very good point to be made!

Diving Nitrox -- pros & cons

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