Computer help

[kadleck]

is it really that new that u didnt know about it

Having looked into 'air28' a little more, it seems to be limited to SUBEX diving centres, which I have not used. The 'light nitrox' mix has been around since 2006. Quoting from the SUBEX site:

Since the start of the 2006 season, divers at all SUBEX bases have been treated to SUBEX's very own breathing gas: SUBEX air28.

SUBEX air28 is a light NITROX mixture containing 28% oxygen.

This mix of air combines the advantages of 'NITROX diving' (32-36% oxygen) with the use of 'normal' diving air (containing 21% oxygen).

However, the dive computer doesn't need to be switched to a NITROX mixture, but remains in the normal compressed air mode.

For sport divers on holiday, these two measures taken by SUBEX have succeeded in 'squaring the circle'.

and...

The adoption of SUBEX air28 as its standard mix makes SUBEX the first dive operator in the world to launch a new product. Once again, SUBEX has broken down a barrier for the benefit of sport divers on vacation the whole world over.

 

[buleetu]

subex wouldnt be able to provide this air without proper research and testing would they??

why is it so benificial to ''holiday'' divers then? why arent they using it everywhere if its so great

can ye tell the differance when ur breathing full nitrox 32-36 compared to ordinary air, i mean does it taste different or something and can dives last a whole lot longer on full nitrox

 

[Quaack]

Nitrox reduces nitrogen loading, extending bottom time & shorter surface intervals.
The trade off if reduced max depth.
The greater the mix, the shallower the max depth.
Just don't exeed the mod for the mix, & you will be fine.
Take a nitrox course after your trip, then you will better understand.

Dave

 

[scubadiver888]

quote"If you're definitely using an enriched mix (you say 28%), the computer needs to be set the same, otherwise it will not calculate correctly. Also, if you've not had nitrox training, you should be on 21%O2 (air), so this is a little confusing!"

this 28% air thing is new i guess, when u said it was nitrox earlyer i went down to the centre to find out some more, they say its a mild nitrox mixture theres a q&a below about it if u have time to read it

im not nitrox trained at all, i didnt intend using 28% but thats all they have down there,no 21% they say its fine for a non nitrox diver to use this stuff, my instructor told me to keep my computer set to 21% for conservatisims sake
thanks kadlack

If you go to SUBEX Red Sea Diving Centers and read about Subex air82 they CLEARLY state it is Nitrox.

If you are not Nitrox trained and you are diving with Nitrox you have no idea what the dangers are. This would be the same as taking an average person off the street, giving them a resort course on scuba diving and telling them they are certified. It is, in my opinion, totally irresponsible.

If you have not been trained on oxygen toxicity, how will you know if you are exceeding limits? Did you sign a waiver? Every dive operation I've been with has me sign a waiver indicating I understand the risks of diving and I'm responsible for myself. If someone said, "All we have is Subex." I would be unwilling to sign the waiver without the appropriate training.

Hopefully, you are always diving with an instructor or guide and they are monitoring things to ensure you are within limits.

If you dive with Subex and have the computer set to air, the nitrogen loading information will be wrong BUT in your favour. If all you have to worry about is the nitrogen loading then this is fine. How do you know your o2 saturation levels though?

Additionally, if the computer is telling you about your o2 levels, it is NOT set to air.

 

[vshearer]

From the manual:

Oxygen toxicity (CNS O2% LIMIT)
Oxygen toxicity is calculated on line as a function of depth values and the preset gas mixture. If the partial pres-
sure of oxygen rises above 0.5 bar, the CNS O2 value increases, if the partial pressure of oxygen is below 0.5 bar,
the CNS O2 value decreases.
The CNS O2 status will only be displayed if higher than 5%. During the ascent the display of the oxygen toxici-
ty is replaced by the ascent rate. See also ->Nitro

I think your alarm was due to another factor.

 

[katdiver]

I'm sure I've seen my Aladin give me 5% O2 in the past after doing deep dives on air. Basically they've chosen a mix that can be used at recreational depths that reduces the nitrogen intake. Diving it as if it was air just makes that even more conservative. Sounds like a win/win situation.

 

[buleetu]

quote''Hopefully, you are always diving with an instructor or guide and they are monitoring things to ensure you are within limits.''

its against the law to dive in egypt without an instructor,or at least if its not against the law its not a practice they partake in unless your a very capable diver

according to all the information ive so far read this mix is fine for me to dive with concerning my training, i will however take ur advice and do a nitrox course when im home,thank u quaack

quote from the aladin manual
"Nitrox
Nitrox is a gas mixture consisting of nitrogen and oxygen. The kind of air used for diving with compressed air is
the same as the normal air of the earth‘s atmosphere (78% nitrogen, 21% oxygen and 1% inert gases). Therefore,
normal air is also Nitrox!"end quote

it also says this
"Aladin® Air Z Nitrox considers the short term toxic effects of oxygen (CNS damages) by means of the so called
"oxygen- clock". It is based on a list which shows the units of toxicity for oxygen per unit of time and is dependent
on the ppO2. The indication of toxicity is shown as "CNS O2 %" (= relative toxicity of oxygen for the central
nervous system). CNS O2 = 0% reflects a normal physical state before the first dive, CNS O2 = 100% reflects the critical upper limit-"

so the 5% reading i got if acceptable yes?? what i wanna know now is how to avoid getting this reading at all,

they say on there website {thank you for the link scubadiver888} that this 28%air makes divers far less susceptible to dcs or oxygen poisoning

note the far less, obviously theres still a risk, so as a non nitrox trained diver using a mild nitrox like air mixture how do i avoid getting into trouble with oxygen toxicity

 

[kadleck]

Therefore, normal air is also Nitrox!

They are right, of course, in that any mix of nitrogen and oxygen is 'nitrox'. But what is generally (and yes, lazily) referred to as nitrox (including the 'Nitrox' setting on a computer) is actually EANx - short for Enriched Air Nitrox, where the air is enriched with added oxygen (thus reducing nitrogen percentage). Clearly, 28% O2 is an enriched mix, but not very enriched. The fact that they also have you diving with the watch set for air does have an added bonus, in that you are reducing nitrogen exposure still further. So it does sound like a win-win. My only niggle is with the watch not set for 'Nitrox' means it is not monitoring the increase in oxygen exposure. But it is, as they say, a 'light' mix, so is probably OK.

note the far less, obviously theres still a risk, so as a non nitrox trained diver using a mild nitrox like air mixture how do i avoid getting into trouble with oxygen toxicity

[caveat!]I am no expert[/caveat!], but I really doubt whether this mix will get you in trouble with oxygen toxicity. I'd be happier having them set your computer for nitrox though, so it is at least measuring it!

 

[buleetu]

ill ask them about setting the computer before my dive today thanks for the advice

the mod with this mixture is 40 metres, is the mod of eanx less because of the oxygen content yes? whats the max operating depth of 32 and then 36 ?

the partial pressure of o2 is what causes the problems here isint it, does the oxygen compress or something and make it more concentrated going into the lung

 

[kadleck]

You have clearly seen the trade-off. Higher O2 % allows increased bottom time (due to decrease in nitrogen), but a shallow max depth (due to oxygen toxicity, which can cause convulsions).

I found this (very old) thread which has a formula which returns the MOD in feet:
http://www.scubaboard.com/forums/archive/index.php/t-8471.html