YD Scuba Diving Forums banner

1 - 8 of 8 Posts

·
Resident Taste Tester
Joined
·
639 Posts
Discussion Starter #1 (Edited)
Whilst beedling about in goldonbog yesterday afternoon a couple of things came to mind. One of these things I have forgoten at the moment, but it may come to me by the end of writing this :D

The one I cna remember though, as I used the last of my 15s contents in the 33 minutes we'd been in the water was...
If I was using a richer nitox mix - I had gods nitrox in my cyl - would I have a better consumption rate? ie would I be able to utilise one of the advantage that using nitox is reputed to give. eg more time wiothout deco.

My second thought was of equally earth shattering importance, but I can't for the life of me remember it now :( ah well
 

·
Registered
Joined
·
368 Posts
I think(?) the question is 'does using Nitrox improve your consumption rate?'.

If it is, the answer is no, it doesn't.

If that wasn't the question, I'll join Scubadog in waiting for enlightenment :)
 

·
"Three sheds"
Joined
·
12,688 Posts
Beardy said:
If I was using a richer nitox mix - I had gods nitrox in my cyl - would I have a better consumption rate?
The amount you need to breath is controlled more by the body's need to expel carbon dioxide than lack of Oxygen.

On the surface you breathe in 21% O2 and breath out around 16%-17% O2.

At (say) 30m, you breath in O2 at 21%, and breath out around 20% (as the pressure is 4 bar at 30m). Any extra O2 due to Nitrox isn't going to make any difference.

Janos
 

·
Wreck Enthusiast
Joined
·
4,161 Posts
The coffee is kicking in a bit so I think what Beardy is saying is that he was diving on air and would he have been able to stay down longer than 33mins on Nitrox...

...and the answer is not because of Nitrox, no :)

Your bottom time was limited by your gas consumption so if the only difference was using nitrox instead of air then you'd have used 15L of nitrox instead. However with Nitrox you would have absorbed less nitrogen than with air, so you ought to be well within no deco limits compared to air.

However if you'd had nitrox, you might have relaxed more thinking that you now had plenty of bottom time and as a result of relaxing your consumption might have been better and you might have had a longer dive - but this wouldn't be an effect of the gas :D
 

·
Resident Taste Tester
Joined
·
639 Posts
Discussion Starter #6
Thanks all. I was asking if nitrox would improve my consumption, but it was late and I probably wasn't thinking straight :)

I thought that that would be the answer. Ta.

I've remembered my other thought as well now :)

Do diving computers take into account your body mass? ie do you put your wight into your 'puter for it to be considered by the algorythm? This thought came to me as I was effectivily diving on someone elese computer on Sunday, and I was wondering if my extra bulk would have made what I was doing any more dangerous.
 

·
Shipwrecked & Comatose, drinking fresh mango juice
Joined
·
2,614 Posts
NeilB said:
Nope, computers are based on Mr Average. If you had to put your weight in mine wouldn't let me dive!
yeah, mine too. I'd have it set to 'BSAC Diver' and it would tell me to go and eat some pies.

Seriously, though, this is a whole other subject. The dive pooter is based on a set of algorithms and assumptions and it's up to you to decide if you want to accept that or pad it yourself - I dive my trusty old (or maybe it's just 'old') Suunto Solution Alpha with tables and watch as a backup (along with buddys computer). It's an air computer so when I dive with Nitrox I am doing the air profile; the richer my nitrox mix the more 'padding' it is giving me. If I dive air, I set the computer to a more conservative profile.

It's really your choice but I would recommend a nitrox course as it will give you a whole lot more information about the physiological effects of gases on your body. I did the basic TDI course - 1 day, open book exam, no dives and it certifies me to use up to 40% nitrox. I don't use it to extend my run times, I use it for the post dive effects - after a couple of dives on nitrox I am safe to drive home, whereas on air I may not have been! Having said that I don't use it to extend my run times, as was alluded to earlier in the thread, I have found that my consumption has gone down; probably a combination of being more relaxed in the water through experience as well as knowing I have something of a saftey factor built in.

Hope this helps

Andy
 
1 - 8 of 8 Posts
Top