The narc fairy comes to visit....

Bythesea

Bythesea

New Member
I have always stated that in the best part of two decades of OC diving that I have only ever noticed being narced once this was at the best part of fifty metres on air, single 12, no redundancy...ahh, the good old days... in Wastwater I know I was narced as I was flying around, arms out humming the dambusters theme...

Dah dha dum dah dum dah dha dah...

I recognised the signs... eventually, and made some upwards movement so my head cleared.

This was early in my diving life so I do know what narcosis feels like and I maintain that this has been the only genuine time I have been narced, others may disagree.

On Saturday I took me and my new to me rebreather on a 40M dive, air dil, I have had it to 35M, no noticeable head mush to report and most of this dive was around 32-35, all was well with the world.

At the turn point we dropped off a ledge at the edge of the reef down to 41, round a rock and back up to the plateau. There was a massive difference in my mental state between 35 and 40, I could really feel it come on and then disappear just as quickly. It was really odd, very obvious and very instant.

It is fair to say that sub 35 will be reserved for helium on the box from now on...
 
Only the dambusters theme? Only a nip at the bottle then.

I clearly remember The Ride of the Valkyries at full volume when using a sledgehammer to knock portholes off the 'Doria on air... at 220 (feet naturally). The bravery of youth, and not having any other options...


Qucik math test: At what depth using air as diluent and a 1.2 PP02 setpoint does your rebreather become MORE narcotic than breathing air open circuit?



:720icon:

Dave


.
 
Last edited:
matthewoutram said:
>47m

Do I get a lolly-pop?
Click to expand...




No, just the coveted "Diver Dave Seal of Approval", generally awarded for new homebuilt rebreather bits, but hereby now awarded for being able to do the math without reversion to use of toes to carry forth the decimals...


:trophy:


Well done!

Dave

.
 
Dave Sutton said:
No, just the coveted "Diver Dave Seal of Approval", generally awarded for new homebuilt rebreather bits, but hereby now awarded for being able to do the math without reversion to use of toes to carry forth the decimals...


:trophy:


Well done!

Dave

.
Click to expand...

:-)

...and in case anyone needs it: (ppO2 / FO2) = D(bar)

Deeper than this depth ppO2 (from diluent) goes over SP and is subsequently breathed down and replaced by diluent (in this case Nitrogen as it is air).

Matt.
 
Last edited:
[/QUOTE]

I remember hearing church bells and thinking that was the signal to go home at 60-ish metres on a wall on air. When I got to my first Pyle stop and looked at my computer I, er, noticed the max depth had actually been 89m.[/QUOTE]


Nice...

Air seems to mimic what nitrous oxide does at the surface.. based on my informal experiments here with a tin of nitrous donated by a friendly dentist for the occasion. Makes sense, air is nitrogen and 02 as a mixture, nitrous oxide the same as a compound. Studying nitrous oxide intoxication, one of the symptoms is auditory hallucinations, which is what our "study group" here all observed. I remember as a kid hearing what seemed to be someone pounding on the wrecks with a huge hammer as I reached 100 feet or so... later on I realized that it was my hearbeat and the sound of the blood rushing thru my eardrums (no joke). At 200 feet I hear the tinkling of crystal glasses... at 250 the "wah-wah noise" that Anne Marie famously described sound dominates all. This is just me, actual mileage may vary.

I never really "got" narcosis intelectually until I started doing lots of dry chamber dives: It was VERY clear at 165, and made us unable to function at 250. Then once I "knew" my symptoms I could begin to detect it at 40 feet in the dry chamber. Even now I can still detect it tha shallow, and I chalk it up to having had the opportunity to do a lot of dry hyperbaric dives. I think that the "noise of the environment" hides it a bit in the water, but that it's there nonetheless a lot shallower than people think.


If you ever have a chance to safely play with nitrous oxide in a controlled environment, it's a really valuable tool for understanding narcosis.

Dave

.
 
Last edited by a moderator:
Dave Sutton said:
Qucik math test: At what depth using air as diluent and a 1.2 PP02 setpoint does your rebreather become MORE narcotic than breathing air open circuit?
Click to expand...

matthewoutram said:
>47m
Click to expand...

matthewoutram said:
...and in case anyone needs it: (ppO2 / FO2) = D(bar)

Deeper than this depth ppO2 (from diluent) goes over SP and is subsequently breathed down and replaced by diluent (in this case Nitrogen as it is air).
Click to expand...
I assume you guys don't regard O2 as narcotic for any of this to be relevant (or factual)?

I'm not convinced either way, but I've always calculated narcotic depth as if it is. So, for me, nitrox is as narcotic as air, regardless of depth.

But then, I don't use air as diluent at any depth.
 
nickb said:
I'm not convinced either way, but I've always calculated narcotic depth as if it is. So, for me, nitrox is as narcotic as air, regardless of depth
.
Click to expand...


Based on having done 100's of open circuit dives in the 100-120 foot range on both air and using 32% (don't do the math... I know what it adds up to), I can say that narcosis is far less there on 32% than on air.

Not going to get into 0xygen as a narcotic, but my own limited empirical experience does not support the hypothesis.



Dave

.
 
Dave Sutton said:
Based on having done 100's of open circuit dives in the 100-120 foot range on both air and using 32% (don't do the math... I know what it adds up to), I can say that narcosis is far less there on 32% than on air.

Not going to get into 0xygen as a narcotic, but my own limited empirical experience does not support the hypothesis.
Click to expand...
Tricky one this. I felt the same way when I started diving nitrox, but thought it could be explained by me becoming a more experienced diver. I never went back to using air, so couldn't compare. I used some pretty lean nitrox mixes though and couldn't say it felt any different.

Air as diluent though is a whole different kettle of fish. I hate it at any depth and put the narcosis down to WOB.
 
nickb said:
I assume you guys don't regard O2 as narcotic for any of this to be relevant (or factual)?

I'm not convinced either way, but I've always calculated narcotic depth as if it is. So, for me, nitrox is as narcotic as air, regardless of depth.

But then, I don't use air as diluent at any depth.
Click to expand...

No, I don't subscribe to that. It's not my experience. YMMV.

Matt.
 
matthewoutram said:
No, I don't subscribe to that. It's not my experience. YMMV.
Click to expand...
My mileage has no opinion either way really, as I said above.

However, many people's experience doesn't tally with reality. The internet is awash with heroes that have never been narc'd or say that 50m on air never did them any harm. Subjectivity is remarkably inadequate for measuring many things.

Oxygen has properties that would seem to lend themselves to inducing narcosis and that's good enough for me to include that possibility in my calculations. I could still have used 25% at 45m when I was diving OC and reaped some benefit over air, but I'd still have been dysfunctional. Anything over 40m was enough for me to want to use some helium, regardless of the conditions.

With closed-circuit, even 30m with air dil is unpleasant, so the calculation above is just a game but I hope you enjoyed your lollipop ;)
 
You must log in or register to reply here.
Back
Top