How does Nitrox work?

I'm a new diver and have no reason to know this just yet but I'll ask the question out of pure curiosity:

I'm told Nitrox extends your bottom time. Exactly how? Or more to the point...why isn't all air created equal?

Thanks,

Mark

air is 21% O2 and 79% Nitrogen (roughly)

nitrox, or enriched air, is when you add more O2 to air (i.e. you "enrich it" with O2). you can end up with, say, 32% O2 and 68% Nitrogen. notice you've dropped the Nitrogen 9% by increasing the O2 9%.

that diminution of Nitrogen means that you are absorbing less Nitrogen as you breathe under water. that means that you have a longer time before your tissues get "saturated" with Nitrogen, and thus you have a longer dive time with 32% Nitrogen than if you were using 21% (i.e. air)

simply put

less nitrogen in a mix = more bottom time at a given depth

here's a pretty comprehensive FAQ:

http://www.gasdiving.co.uk/pages/misc/Nitrox.htm

You're going to get a lot of very specific, scientific answers one this one.

Long and short is if you increase the concentration of oxygen, you're decreasing the concentration of nitrogen. So the lower concentration of nitrogen means there is less nitrogen for your body to absorb, therefore increasing your bottom time before your enter into decompression.

MarkSteffen:

I'm a new diver and have no reason to know this just yet but I'll ask the question out of pure curiosity:

I'm told Nitrox extends your bottom time. Exactly how? Or more to the point...why isn't all air created equal?

Thanks,

Mark

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Extended bottom times are a theory for most recreational divers. What I mean by that is diving Nitrox within recreational limits may allow you to stay down longer - but usually you'll run out of air before reaching the full benefit of diving Nitrox - purely as an increaser of bottom time.

In a similar way it can be used to decrease your required surface interval time.

Paddler3d appropriately pointed out the simplicity in how it works... so I wont reiterate that - the bigger question is do you as a recreational diver need it and is it worth the extra money you'll spend obtaining it?

Generally speaking the answers to those questions for most recreational divers is NO and NO.

A lot of research has been done on this and everyone who's been diving a while has an opinion on it. DAN (Divers Alert Network) has clearly stated in the past that Nitrox is of little use and little benefit for most recreational divers.

The exception to this rule is for those doing multiple dives over multiple days... such as on a week long vacation where you're diving 3 or more dives a day for 3 or more consecutive days.

It is not a "deep" gas and in fact becomes dangerous the deeper you go due to the increased risk of oxygen toxicity.

Once you've decided on the type of diving you'll be doing, then you can worry about Nitrox. The unfortunate thing in this industry is that most dive shops routinely push this course on people as a "need." It is far from needed, so don't be fooled into a class for taking a class sake.

I've got no problem with people who it will benefit taking the class... but most new divers... and even many experienced ones don't fall into that category.

offthewall1:

Extended bottom times are a theory for most recreational divers. What I mean by that is diving Nitrox within recreational limits may allow you to stay down longer - but usually you'll run out of air before reaching the full benefit of diving Nitrox - purely as an increaser of bottom time.

Click to expand...

yes and no. diving to 70 feet on air, you have a max of 40 minutes bottom time; diving 32% it goes up to 60 minutes; using 36%, your bottom time goes up to 75 minutes.

while it's true most divers probably won't be able to dive the full 75 minutes, most divers will be able to dive, say an extra 10 or 15 minutes on an AL80

at least that has been my experience. i did see an increase in my bottom time, particularly when diving tables.

I thought H2Andy's reply was pretty simple and non-scientific!

Percentages were sometime around 5th or 6th grade - At least in 1963 they were!

rather than "most recreational divers" I would say "most new recreational divers." As people get more experience their gas consumption goes down, and some people are just naturally fish. While the multi-day multi-dive thing is an obvious win, I imagine plenty of folks can take advantage of the increased bottom time on 1-2 dives (as said, especially with tables.)

Most of the people I dive with would end up in deco on most of our dives without Nitrox. Anybody with a reasonable (.75 or less) SAC rate, doing terrain-based dives with a max depth of 100 feet, is going to push limits or exceed them on air. (Maybe not true on an Al80, but nobody up here dives those tanks. On a 95, 100 or 130? Easy.)

offthewall1:

Once you've decided on the type of diving you'll be doing, then you can worry about Nitrox. The unfortunate thing in this industry is that most dive shops routinely push this course on people as a "need." It is far from needed, so don't be fooled into a class for taking a class sake.

I've got no problem with people who it will benefit taking the class... but most new divers... and even many experienced ones don't fall into that category.

Click to expand...

I am the last person to endorse the dive industry's penchant for marketing useless classes, but I disagree that nitrox falls into this category. A greater understanding of how compressed nitrogen and oxygen affect our physiology should be part of every diver's education. In fact, these easily understood concepts should be included in basic open water classes, in my opinion.

Cheapest, easiest, and in many ways rewarding card: $100 - 3 hours class in many places. Sorry to see Inst-offthewall1 talk against it. Get your AOW & Nitrox cards ASAP. Too often divers "wait until they need one" but don't have it when they actually do.