Nitrox vs Air

[skipjack28]

excuse me but my understanding is that 100% oxygen
will burn your lungs. It is far to rich to breathe
without some nitrogen mixed in. The highest breathing mixture I have heard of was 80% oxygen.
which would be the inverse of normal air.
As far as getting narcosis that is caused by the partial pressures created by depth. As you go to 100ft and beyond the ratio of n2 to o2 decreases the o2.
Starting out with more o2 balances that ratio at depth.
People get light headed and stupid from a lack of oxygen.

If you want to dive a deep hole or wall at 200ft
then nitrox is a good thing.
above 100ft it is no big deal.
Thats my understanding of it.

 

[Scubaroo]

skipjack28,

You need to read up on modern dive theory.

* 100% O2 is commonly used as a deco gas
* narcosis is not caused by lack of oxygen

 

[skipjack28]

I was confused with rapture.
Mea Culpa

 

[The Iceni]

skipjack28 once bubbled...
excuse me but my understanding is that 100% oxygen
will burn your lungs. . . .

If you want to dive a deep hole or wall at 200ft
then nitrox is a good thing.
above 100ft it is no big deal.
Thats my understanding of it.

hi Sipjack,
On the first point you are quite right oxygen does "burn" the lungs but only after prolonged exposures. You will learn that 50% Nitrox is entirely safe (0.5 bar).

The NOAA limit for continuous oxygen is 1 bar = 1 Oxygen Toxicity Unit per min. => 60 x 24 = 1440 OTUs per 24 Hr period

At higher partial pressures the OTUs per minute are greater, giving maximum permitted exposure of 3 hrs in any 24 hour period, when exposed to ppO2 of 1.3 bar (8 OTUs per minute).

It is not linear.

On the second point I am sure you can work out that Enriched Air Nitrox is NOT a deep diving gas at all. In fact it is recommended by most agencies that the maximum oxygen exposure is limited to 1.4 bar. Even air at 200 ft (66 metres) has a pp O2 of 1.6 bar.

 

[DiverBuoy]

Dr Paul Thomas once bubbled...
Even air at 200 ft (66 metres) has a pp O2 of 1.6 bar.

251.4 fsw - would be 1.6

Using 1.6 PO2 maximum exposure divided by .21 (P02 in Air) = 7.619 ATA times 33 fsw = ~251.4 feet

 

[Uncle Pug]

DiverBuoy once bubbled...


251.4 fsw - would be 1.6

Using 1.6 PO2 maximum exposure divided by .21 (P02 in Air) = 7.619 ATA times 33 fsw = ~251.4 feet

don't forget to subtract 1 ATM for the atmosphere.
(218 fsw)

 

[Rick Murchison]

Dr Paul Thomas once bubbled...
The NOAA limit for continuous oxygen is 1 bar = 1 Oxygen Toxicity Unit per min. => 60 x 24 = 1440 OTUs per 24 Hr period

That's for a single exposure of one day...
NOAA limits for multi-day exposures start at 850 OTU's for the first day and drop to 300 OTU's/day for day 11 on...
(Table 3.6 NOAA Diving Manual)
Rick

 

[DiverBuoy]

Uncle Pug once bubbled...

don't forget to subtract 1 ATM for the atmosphere.
(218 fsw)

yes uncle

 

[douhunt]

Everyone claims that nitrox increases your bottom time, and most certification agencys teach that. It is not true, nitrox only increases your no decompression limits. If a person were to dive to 100' on 32% nitrox there bottom time will not be increased, but only there ALLOWABLE BOTTOM TIME will be increased by longer no decompression limits.

 

[MikeFerrara]

Good point. As far as i know time is uneffected by the gas we breath. if I remember right though velocity can effect time as described in theory of realativity.

What gas can I breath at work to shorten my tme?