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Hi Brock,
You ask ...
<< A couple of my favorite sites (Oronogo, Lake Elmer Thomas) and some
I've
yet
to visit (Cannonball Springs, Ribidoux Springs) require a hefty walk/climb
to a parking lot- easily 300 ft on a steep incline with no shade. I've
adopted Scott's recommendations and they seem to help. Over a
multi day visit (I've some training coming up)- do I place myself at some
danger doing this? >>
From what I understand, in most cases I see no real problem with breathing
oxygen or a high oxygen mix on the surface if it makes you feel better. The
max PP(O2) you'll get is 1.0 ATA from the pure oxygen and 0.5 ATA from EAN
50. So you use up the oxygen clock at around 0.3 %/min. at 1.0 ATA and 0.1
%/min. at 0.5 ATA. So if it takes you 30 minutes to get your stuff to the
car, you have added around an extra 10% to the CNS oxygen clock by breathing
pure oxygen and around 3% for EAN50. You need to decide if that's important.
By the way, the previous numbers are based on the NOAA limit of 5 hours
allowed for the CNS oxygen clock for a PP(O2) of 1.0 ATA. But have you ever
been in the burn ward of a hospital? You may see people in oxygen tents
breathing pure oxygen for two weeks in a row. You make up your own mind on
the level of conservatism that you want to accept.
Pulminary oxygen toxicity almost never comes into play for the type of diving
you're doing.
And always remember, that the advice you recieve from me is worth what you're
paying for it.
Take care and dive safe, Scott
In a message dated 8/20/00 12:45:08 PM, Bfrede1615@em*.ms*.co* writes:
<< OK: I asked this on Steve Lewis' Techdiver.com and I'll ask it
over
here
First I'll cite Scott Gudmundsens' text, then give my situation. It's
really
not a "Yes, but..." situation, rather I've adopted this for some of my dive
sites , and wondered if over a period of days if this might cause problems
I quote: "A tip for Nitrox divers!
If you're going to pack your gear directly to the car after surfacing and
taking off your fins, continue to breath your high 02 mix all the way to the
car! You'll be amazed at how much more energy you'll have!
Try this experiment. Hike halfway to the car while still wearing all your
gear except fins, while breathing enriched air. Halfway to the car, spit out
your regulator, and breath 21% for the second half. You'll have trouble
making it without a rest! Try this breathing 100% 02! You can practically
run all the way with 100 lb. on your back!
Safety Tip:
If you've pushed the no decompression tables, are chilled, or missed a
safety stop, don't try to pack your gear to the car immediately after
surfacing. Exercise speeds bubble formation in the bloodstream. Sit still
and rest for twenty or thirty minutes and breath your 100% 02 (if you have
it), or breath Nitrox. Then take it easy packing your gear to the car. Take
many light trips, not one big heavy trip."
*************************************************************************
and here are Steve's comments on CNS toxicity:
"Please do not confuse Pulmonary Toxicity with Central Nervous System
Toxicity. This must be tracked on every dive. CNS Toxicity is a result of
very high levels of oxygen >1.0 ATA for relatively short periods of time
(the ubiquitous 1.6 ATA for 45 minutes routine from NOAA) To be safe, may
authorities recommend keeping one's CNS clock at < 80% over a 24 hour
period. I would personally recommend tracking CNS very, very exactly for
every dive... CNS will get you killed."
A couple of my favorite sites (Oronogo, Lake Elmer Thomas) and some I've yet
to visit (Cannonball Springs, Ribidoux Springs) require a hefty walk/climb
to a parking lot- easily 300 ft on a steep incline with no shade. I've
adopted Scott's recommendations and they seem to help. Over a
multi day visit (I've some training coming up)- do I place myself at some
danger doing this?
Any and all replies are welcome.
Thanks in advance
Dive Safe
Brock Frederickson
Bfrede1615@em*.ms*.co*
www.uwservicesllc.com
----- Original Message -----
From: <ScottBonis@ao*.co*>
To: <techdiver@aquanaut.com>
Sent: Saturday, August 19, 2000 10:09 PM
Subject: Oxygen measuring (was "OMS Like" DIN flow regulator)
> Hi Paul,
>
> You are correct in that if gas is flowing out to the ambient air, the
> pressure must be somewhat above ambient. The trick is to make it as
little
> above ambient as possible and yet still have gas flowing. Many divers
choose
> to use some form of flow meter or flow control device while a bunch of us
> older guys simply turn the tank valve gradually closed until we can just
> barely hear the gas flowing.
>
> Chris Elmore has mentioned that it is the partial pressure of oxygen that
the
> sensor is responding to. And we know from Dalton's law that the PP(O2) is
> equal to the fraction of oxygen in a gas multiplied by the total pressure
of
> the gas. So if the gas pressure at the sensor is above ambient and
ambient
> was the pressure at which the sensor was calibrated, the sensor will
measure
> a higher partial pressure of oxygen and will therefore display an
> artificially high fraction of oxygen for the gas under analysis.
>
> If these terms are not familiar to you or this explanation is difficult
for
> you to understand, then I recommend strongly that you take a course in
Nitrox
> diving. It really is the best way to start learning about the use of
gasses
> other than air for diving. You can get some good information from these
> lists, but occasionally you can get some bum dope also (of course never on
> "techdiver.")
>
> Take care and dive safe, Scott
>
>
> In a message dated 8/18/00 1:10:30 PM, Bakalite@ba*.co* writes:
> << I guess this doesn't make sense to me. If gas is flowing, how can
> the pressure be ambient? What is the error induced by having a
> higher PP due to a flow over the element versus a resing pressure.
> It seems to me that if the flow is off by 10% you'd get a 10% reading
> error, although in practice this doesn't seem to bear out. Sorry if
> these are stupid questions, but I'd rather ask some of those than tox
> on o2.
>
> Thanks.
>
> Chris Elmore wrote:
> ~
> >Paul,
> > For flow rate, get a needle valve from the brass fittings
> >section at Lowes and use a flow meter to calibrate it. Once it's
> >calibrated epoxy the adjustment shaft and you're set to go- total
> >cost: about $5. You can even oxygen clean it if that makes you
> >happy. Flow rate doesn't really matter as long as you have enough to
> >purge the lines and move the gas over the sensor but not enough to
> >produce back pressure. Sensors measure partial pressure so you have
> >to keep the pressure at ambient. If you can hear gas flowing that's
> >enough.
> >C.
> --
> Paul Braunbehrens mailto:Bakalite@ba*.co*
> http://www.daw-mac.com Mailing list for digital audio on the mac >>
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