Why Nitrox

[cummings66]

You'll hear that until you can reach the NDLs for diving on air, Nitrox is useless. But that fails to take into account the reduced SITs you'll have. Diving nitrox might allow you to get in 4 or 5 dives where you'd only get the chance for 2 to 3 otherwise, by reducing that surface interval.

As for its effect on narcosis, reducing nitrogen will reduce the narcotic effects of NITROGEN but oxygen is thought to be narcotic too. So NITROX's effects on narcosis isn't known.

I'm going through the program now and my book says that it does not reduce the effect of Narcosis from the nitrogen. It also says that you should allow 1 hour surface intervals so you don't really have a shorter SI if you use tables.

Now what does change it is if you use a computer in which case you can get more dives in.

I would agree with those that say until you can hit the NDL on air it's not of much benefit, I can hit them so it's useful to me.

A random poll of the divers I know suggests that many of the claimed benefits such as being less tired are all in the head. I don't get tired on air so I know it's not going to do much there, and my instructor says he doesn't notice any effect on him by diving it either.

You'll find proponents in both camps, some say it helps and others say the only benefit is longer bottom times. It's like the argon in the drysuit argument...

 

[radinator]

I agree that looking at the surface while ascending is hypnotic. I love doing it that way.

 

[aedavidson]

I am not sure if it is just in your head but I do feel better with Nitrox after multiple dives. I was on a liveaboard last month in Belize did five dives most days, all at least an hour with a steel 95. Mostly shallow but got down to 100' on some of the walls. I was diving 31-34% depending on the fill. I felt great and was ready to go for the night dives and some on air were not. I know that everyone is different but when diving from a boat on air after a two tank and a night dive I am ready for bed. I also never came close to my limits on nitrogen. I like the idea of looking up as I like to ascend slowly I will have to try that.

 

[Diver Dennis]

I feel better if I do 3 or 4 dives a day but 2 feels the same to me.

 

[Cacia]

I get headaches on air after three dives. I feel better on Nitrox. ...But i am a highly tuned machine.

 

[Pyrofish]

I'm going through the program now and my book says that it does not reduce the effect of Narcosis from the nitrogen. It also says that you should allow 1 hour surface intervals so you don't really have a shorter SI if you use tables.

Yeah, I was told the same thing in class, but when we did the dives, for the class, I think we did a 30 minute surface interval. The tables allow you much shorter surface intervals than 1 hour. I think there is a thread about that somewhere on the board. I remember seeing it last year. I don't have my tables in front of me, but for one particular set of dives I was planning, 3 dives to 60', according to the table for 36 IIRC, it said I could do 30 minutes down, 20 minutes up, 30 minutes down, 20 minutes up, 30 minutes down. Like I said, I don't have the tables in front of me, but I think total O2 exposure for the day would be 45%, and it would be the last dive for the day.

So I don't know what's up with the one hour SI. It was mentioned in class, but was not followed in practice. I don't believe it was followed in the examples either. I could very easily be wrong though
Jason

 

[Packhorse]

How much does it cost for a full of air vs Nitrox?
Here I pay $5NZ at the LDS or upto $7NZ at more remote locations for air.
The LDS is putting in Nitrox equipment and has said about $20NZ for a full. At that price (and $390 for the course) I dont think i'd be in any hurry to use it.

 

[DandyDon]

Originally Posted by DandyDon
Request 28%.

For your own good, take the course. Let's learn what we're doing, OK?

Well sure take the course - something wrong with my post, tho...?

The immediately following post went into more detail...

Yes it will, but you will need to operate with a relatively lean nitrox mix. For a 40 meter dive (roughly 130') at a partial pressure of 1.4 PPO2 (Which is the recommended pressure for the working portion of the dive), you can use a 28% mix. This reduces the N2 exposure by a little less than 10%, (Normal exposure fN2 79% - Current exposure fN2 71%) which will give you a little less narcosis and a little more bottomtime. It will effectively be like diving to 36 meters in terms of N2 absorbtion

Except Nitrox doesn't reduce narcosis, depending on whom you quote.

How much does it cost for a full of air vs Nitrox?
Here I pay $5NZ at the LDS or upto $7NZ at more remote locations for air.
The LDS is putting in Nitrox equipment and has said about $20NZ for a full. At that price (and $390 for the course) I dont think i'd be in any hurry to use it.

$20Nzd = $13.37Usd - Yeahd that's high. We expect to pay $5 to $8 Usd additional for Nitrox on charters, or I suppose $10-13 Usd for straight fills including tank rental, altho I never get my Nitrox locally - only on charters after traveling, so I could be wrong.

In Cozumel, expect $10 Usd additional, or about $15 Usd total - there you see a lot of resistance, cutting back to one tank a day. On Roatan or Utila - $100 Usd extra for unlimited use for the week, not bad.

 

[PaulChristenson]

Increased bottom time? I just took the class 'cuz I like putting big green stickers on stuff.
(j/k)

I took the class because I wanted to buy another gadget...O2 analyzer...

Paul in VT

 

[clarktenk]

Upon what do you base that belief?

It's not a belief it's scientific fact. Take the course again and you'll see for yourself.

It's really quite simple all you have to understand is the amount of energy that goes into ongassing and offgasing the nitrogen. If you do a dive to 100 ft on air for 15 min and then do the same dive on ean 32 your body will have to ongas less nitrogen and by that measure offgas less nitrogen. The main reason we use nitrox is limit our exposure to the nitrogen.