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Re: On board fires
Just wanted to make a comment regarding Nitrox.....(seeing how I'm a
Nitrox
instructor :-)
First of all, Nitrox is simply oxygen enriched air. Contrary to popular
belief, Nitrox is NOT used for deep dives.....Trimix is. (He, N2, O2)
The only thing deep divers use nitrox for is accelerated decompression
at the shallower decompression stops.
The main advantage of Nitrox is that of extended no decompression times
at
recreational depths (<130'). With Nitrox, there is less nitrogen in the
breathing mixture compared to air and since it is the nitrogen content
which
determines the NDL, you get more bottom time with nitrox.
The reason Nitrox is not used for deep diving is 2 fold. First, since
it
has a higher O2 content than air, Oxygen Toxicity becomes a concern.
This
can occur at an O2 partial pressure of 1.6 ATM or above. For straight
air,
this occurs at 218'. The other consideration is Nitrogen Narcosis.
This is
why Trimix is used for deep diving. Trimix for deep diving is usually
hypoxic
at shallower depths to get around the O2 tox problem, and part of the
nitrogen
is replaced by helium to reduce or eliminate narcosis.
Well, I've blabbed enough....just wanted to contribute to an area I have
some
experience in!
Al
DaveIrons@aol.com wrote:
>
> Jon and Rick you have made some good points.
>
<<<<Bunch of stuff snipped>>>>
>
> For the primary fire suppression system, I would think, dry chemical would be
> used only
> as a last resort. Nitrogen may be safer than Carbon Dioxide (CO2). Air is
> 79% Nitrogen.
> Some advanced divers are using Nitrox mix for very deep dives. Nitrogen can
> extinguish
> a flame by depriving it of Oxygen the same as CO2. Water cools the flame.
> Water is
> generally considered the method of choice by fire departments when
> extinguishing fire in
> porous material like wood or paper.
>
> David Irons
>
--
Al Secor ARS: WA3PWX Scuba Instructor SSI DCSI 5528
http://people2.clarityconnect.com/webpages6/wrkdiver