Nitrox discussion (Split from "Reasons not to use Enriched air" thread in Basic)

orch1ds · Aug 18, 2008

A ScubaBoard Staff Message...
Split from Reasons not to use Enriched air thread in Basic Scuba Forum

Gday divers

This is a copied & cleaned up thread thread that was in Basic Scuba and placed it in this forum for further discussion & education. I think i have cleaned it up but if there is anything glaring i have missed please report it or pm me to look it over.

Please note the rules for the new Advance Forum and keep it on topic, relevant and workplace friendly. Name calling is still against TOS and posts will be deleted.

alot of work went into this thread & it has alot of good information and members have reacted positively to it - please use it as an example to mentor and learn is all i ask.

Many thanks

Hello,

I'm fairly new to scuba diving. Started about six weeks ago and have been going nonstop since. This past weekend I finished my Nitrox and Wreck certifications through PADI. I used Nitrox for the whole weekend and thought it was great.

Question: Is there any reason why I should not use Enriched Air for every dive? Is there a reason why I would want to sometimes use AIR opposed to Enriched Air?

From my studys in the Nitrox class it seems ok for me to just stick to Enriched Air whenever I can.

Thanks for your advice... this site is great!

cmk

String · Aug 18, 2008

orch1ds:
Question: Is there any reason why I should not use Enriched Air for every dive? Is there a reason why I would want to sometimes use AIR opposed to Enriched Air?

Yes. If you don't know the exact site or depth in advance Nitrox can limit you.

No point turning up with a nice 32% mix then finding out its a 40m wreck dive and so on. Lots of times here sites are chosen when on the water and changed at last minute depending on conditions en route.

As to why you'd use air - anywhere below 40m as generally then the nitrox mix is so weak its not worth bothering with.

Those are the main reasons i rarely use nitrox - i cant be sure what im diving until on the boat. The other issue is cost as its 3x the cost of an air fill per dive.

Doc Intrepid · Aug 18, 2008

orch1ds:
"Is there any reason why I should not use Enriched Air for every dive? Is there a reason why I would want to sometimes use AIR opposed to Enriched Air?"

There is usually a cost/benefit ratio to most diving - unless someone is giving you the Nitrox for free!

Under most circumstances I'd prefer Nitrox, for many reasons - some of which might include factors like age.

But there are some unusual types of diving out there. I spent several years on Guam. One of the hobbies of a number of divers there was shell collecting. Divers might spend two or more hours in about 8' of mid-80's degree water at night with a flashlight, looking for unusual shells. After a couple hours you'd get cold and get out, but for shell collecting in 8'-10' of water there is no particular reason to use anything more expensive than air.

Like most things in life, the choices you make often depend entirely on what you're doing, when, where, and why.

Regards,

Doc

InTheDrink · Aug 18, 2008

One of my main fears when diving Nitrox is a strong down current. Mainly cos I tend to end up around 30m in strong currents, tho usually on 32 rather than 36. But still around the 1.4 area. Which is very safe. But wouldn't be ten metres lower. That is my main reason why I have to think about whether to dive Nitrox or not.

Really it's a very specific depth range. Between 20 and 30m it rocks. Shallower than that what's the point given the expense. Deeper than that you need to rethink. So in that 10m zone (which for recreational diving is a BIG zone) it's great.

Personally I love it but when I get near the limit it does up my anxiety a little.

J

InTheDrink · Aug 18, 2008

One other thing, and nothing scientific about it, I don't get headaches on Nitrox. I do on air (and no, it's no skip breathing).

Gombessa · Aug 18, 2008

If you feel narced, ascending slowly is supposed to help "clear your head" pretty quickly. I think the onset of oxygen toxicity is sudden loss of consciousness and involuntary seizures. It's hard to self-rescue from that. I'm sure some more knowledgeable members can say whether there are any indicator or precursor symptoms.

tschmitt · Aug 18, 2008

tfsails:
I was gonna say that diving nitrox beyond the MOD will either get you in a hospital or in a graveyard, but you beat me to it.

You're more likely to end up buried than in the hospital. Seizures as a result of OxTox are not particularly harmful aside for the small and unfortunate side effect - spitting out your reg and sucking down water...

JClynes:
One of my main fears when diving Nitrox is a strong down current. Mainly cos I tend to end up around 30m in strong currents, tho usually on 32 rather than 36. But still around the 1.4 area. Which is very safe. But wouldn't be ten metres lower. That is my main reason why I have to think about whether to dive Nitrox or not.

Really it's a very specific depth range. Between 20 and 30m it rocks. Shallower than that what's the point given the expense. Deeper than that you need to rethink. So in that 10m zone (which for recreational diving is a BIG zone) it's great.

Personally I love it but when I get near the limit it does up my anxiety a little.

J

The MOD of 1.4 ATA is pretty conservative, but I'm not sure I want to dance with the devil either. If I'm doing a bunch of dives at 40-90 ft. I prefer EANx. Personally, I do not get as tired after repetitive dives on it as I do with Air. 90ft and below, Air only for me.

Blackwood · Aug 18, 2008

Gombessa:
If you feel narced, ascending slowly is supposed to help "clear your head" pretty quickly. I think the onset of oxygen toxicity is sudden loss of consciousness and involuntary seizures. It's hard to self-rescue from that.

Not to mention that ascending won't necessarily stop or prevent a seizure.

People have toxed well after leaving the maximum PO₂.

tschmitt:
90ft and below, Air only for me.

Interesting... that's close to the depth (120+) at which I'll no longer consider air as a viable gas.

tschmitt · Aug 18, 2008

Blackwood:
Not to mention that ascending won't necessarily stop or prevent a seizure.

People have toxed well after leaving the maximum PO₂.

If you aren't at 100% of your O₂ Clock and simply a CNS seizure from a high PO₂ then ascending will likely reverse the seizure. If you've been diving on EANx all day and you're pushing 100%+ O₂ toxicity, you probably even run the risk of seizing at the surface.

Blackwood:
Interesting... that's close to the depth (120+) at which I'll no longer consider air as a viable gas.

Sorry, I meant to Rec dive limits.

Anti-Hero · Aug 18, 2008

1.4 ATA is VERY conservative. I personally do not exceed 1.4, but many navy divers at one point in time pushed the 2.0 ATA limits. I think 1.4 is made exceptionally safe so the general recreational community isn't toxing left and right; opening PADI, et. all up to lawsuits.

Nitrox discussion (Split from "Reasons not to use Enriched air" thread in Basic)

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