Nitrox diving

[Superlyte27]

Correct me if i'm wrong, and I know it's a minor point, but less nitrogen means a less lethargic diver. You are being exerted less, and because of that, you are breathing easier.

I don't think it's psychosymatic, but I believe I'm less tired and more efficient when on Nitrox than on air. Whether it's in my head or not, my consumption is slightly less.

Not really enough to make a difference to me.

But another consideration is this. If you are blowing through 77cu' of air in 20 minutes and air costs you 4 dollars to fill. Do you really wanna blow through 77cu' of Nitrox in 22 minutes at a cost of 8 dollars? I don't know what your consumption is, but if your SAC rate isn't below like .8, I'd probably save the money on Nitrox fills until you get more comfortable in the water. Depending on your consumption you might not have gas enough to last into a DECO schedule on air anyway. Just my 2cents mostly based on opinion and assumptions.

 

[liuk3]

For practical purposes, nitrox may not help you much until your breathing rate becomes comfortable enough that you begin bumping against your NDL's on your dives. You'll begin to realize this when you start having to end your dives because of NDL versus gas left in your tank. Over time, everyone's breathing rate naturally slows down as they get more experience and become more comfortable in the water. So, don't sweat it if you're gas consumption is still high at this point.

The other benefit of nitrox is reducing your ongassing of inert gases which reduces your chances of incurring decompression sickness on a dive.

The negative with nitrox is that you need to be trained and not exceed your maximum operating depth when diving this gas mixture.

Have fun!

 

[MXGratefulDiver]

Hi, though there is a near post about nitrox, this question is different.
I'm still a new diver, with only 39 dives under my belt. I'm still an air hog diver, though I realize that I made good improvements.
I will take soon my nitrox class, so I've been reading the nitrox chapter of the NOAA book.

Let's start with a basic statement ... nitrox is simply air with a higher content of oxygen. The purpose of increasing the oxygen isnt to give you more oxygen, but to give you less nitrogen. The reason oxygen is used for this purpose rather than some other gas is simply because oxygen is the second most abundant gas available ... and therefore the least expensive way to do it. From an oxygen-usage perspective, it won't be functionally different than breathing air.

Nitrox gives you more bottom time as there is a lower amount of Nitrogen in the mixture.

Nitrox ALLOWS more bottom time ... within certain limits. It won't GIVE you any more bottom time, if you're bringing the same tank with you on the dive ... because at this point your limitation isn't the type of gas you're breathing, but rather the amount of gas you have available to breathe. And despite anecdotes to the contrary, there is no evidence to suggest that breathing nitrox changes your consumption rate.

But how is the feeling ? Does the diver breath slower or with longer pauses between each breath ?

You breathe as you normally would if you were using air.

Suppose the same AL80 tank but with nitrox. The same volume, the same pressure, but more oxygen. The lungs breath more oxygen in each breath, so the body should have a longer pause to require a new breath owing to the generated CO2. Or you will breath less mixture as in a lower volume there is the same amount of oxygen, or a combination of both things.
Is that how it works ?

No ... it works exactly the same as air. You won't feel any difference.

Does it taste different ?

Tastes like chicken ...

No ... honestly, you can't tell based on breathing it whether it's air or nitrox.

Here is a short article on nitrox that you may find helpful ...

... Bob (Grateful Diver)

 

[emoreira]

.... I don't know what your consumption is, but if your SAC rate isn't below like .8, ......

My SAC rate in in the surroundings of 0,65

 

[TSandM]

Just to correct one statement -- there ARE studies that show that people breathing elevated levels of oxygen will tolerate slightly higher CO2 levels before showing increased respiratory drive. It's not known how or why that works. For a diver, it's not a good thing.

But in general, minute ventilation (the total gas volume that passes through the gas exchange part of the lungs) determines your CO2 levels, and this is functionally independent of the oxygen concentration in the gas being breathed, so long as it is not hypoxic.

So, if you are looking to extend your dive time on a given volume of gas, Nitrox isn't going to do it for you. Becoming a more efficient diver, however, will. If you browse through the New Divers forum, you'll find any number of threads asking about how to reduce gas consumption, and there are a lot of good tips in them.

 

[kanonfodr]

In addition to the great advice about gas consumption and possible ways to improve it, sometimes you are just stuck with "bad" (really just comparatively elevated) levels of gas consumption. The only surefire way to counteract that is to bring more gas.

Example: I dive with a bunch of folks who would drown me on similar tanks, so I bring my LP95s while they are using LP72s, AL80s, and one girl even uses an AL63. We all come out of the water with similar end pressures so everyone is getting their tank's worth, some just need more cash than others do.

Also, you stated you only have 39 dives. Go diving!! I used to obsess over my horrible SAC rate until I just went diving every chance I could get. I've done more dives in the past 2 months than I had in the year and a half previously as certified. My SAC is finally starting to show me numbers that I can be happy with. Maybe in another month or two I can start looking at Nitrox training, since I don't feel the need to spend the extra money to not get too much extra out of it.

In Review: 1.) Bring More Gas. 2.) Go Diving!! Your air consumption is a function of your physiology, but you can certainly do things to improve it (increasing efficiency in the water, increasing comfort, etc). Nitrox is certainly pretty useful, but why use a tool that you can't realize the full benefits of? Air's cheaper, too, and it works just fine for 95% of divers.

Peace,
Greg

 

[Anti-Hero]

Diver efficiency and metabolic efficiency are the two keys to lowering gas consumption. In my personal experience, metabolic efficiency has been the more substantial of the two. I will notice a measurable increase in gas consumption if I've slacked at the gym for even 4 weeks.

The harder I work at cardio training, the lower my SAC becomes without fail. Another noticeable side effect is my resting pulse. When I'm not in the gym regularly my resting pulse is around 65-75 BPM. During periods of heavy cardio training my resting pulse is ~45-55 BPM.

I don't know that resting pulse has any direct effect on SAC rate, but my guess is the lower BPM is related to increased cardio pulmonary efficiency.

 

[Rhone Man]

Just to correct one statement -- there ARE studies that show that people breathing elevated levels of oxygen will tolerate slightly higher CO2 levels before showing increased respiratory drive. It's not known how or why that works. For a diver, it's not a good thing.

Makes sense. I notice my SAC rate drops when I am on Nitrox, but I never knew the reason. I am a chronic skip breather, so it makes sense to me now.

 

[emoreira]

....Also, you stated you only have 39 dives. Go diving!! ....
Greg

It sound easier than what it is in realty for me.
Hopefully I could count more dives.
It's not easy. Far from diving places, hard to find dive buddies, a lot of money and time to go diving, etc.

 

[Mike Boswell]

Just to correct one statement -- there ARE studies that show that people breathing elevated levels of oxygen will tolerate slightly higher CO2 levels before showing increased respiratory drive. It's not known how or why that works. For a diver, it's not a good thing.

But in general, minute ventilation (the total gas volume that passes through the gas exchange part of the lungs) determines your CO2 levels, and this is functionally independent of the oxygen concentration in the gas being breathed, so long as it is not hypoxic.

So, if you are looking to extend your dive time on a given volume of gas, Nitrox isn't going to do it for you. Becoming a more efficient diver, however, will. If you browse through the New Divers forum, you'll find any number of threads asking about how to reduce gas consumption, and there are a lot of good tips in them.

Personally, I can't tell the difference, but I have often heard people claim that they feel they have more energy after diving nitrox than they do after diving air. Is it true that divers using nitrox are "less tired" after a dive? If that is true, what effect would that have on air consumption for subsequent dives?