On Fri, 3 Feb 2006 23:23:13 -0600, "JJS" jschneider@remove socks
cebridge.net wrote:


"Roger" wrote in message news
Then he committed a sin for which job termination is usually
proscribed at most companies now days. You never, ever enter a vessel
that has been N2 purged unless bringing your own breathing air by
tank or hose. He entered without checking the O2 level and almost
suffocated.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com

Roger, did you miss my post and just reply to the response that was snipped by Bryan Martin without him indicating he
did so?

Yup. Never saw it and I *tried" to cover the whole thread.

It was I who filled out and signed the safe work and confined space entry permits. One of my direct reports took the
gas samples with a handheld gas meter. The confined space entry was done correctly per OSHA 1910.146 confined space
procedures. At my place of employment we have to make confined space entries on a routine basis.

As did I, even though at the time I was an Instrument tech. They put
instruments in some strange places. :-))

An attendant was present. An Emergency Response Team was on standby. One thing though, there was no forced air
ventilation. He was using a supplied air respirator (air line mask) with a backup egress system. This was a
professional contract company that does IDLH confined space entries for catalyst work as their sole source of income.
Forced air ventilation will not make a "confined space" a "non-confined space" per OSHA. Ability to egress is a
consideration unto itself. There are permit required and non-permit required confined spaces. (I never liked that
terminology as they both require permits). IDLH atmospheres are permit required.

Roger, I've been reading your posts here for years and you have my respect. It seems as we both have some job
related experience with confined space entries. I've been doing it for 28 years and I sure don't consider myself an
expert on the subject. But please help educate me. Why did the victim go into convulsions instantly if he was
suffocating and why did it take months for him to recover? Like I said, I am not an expert on this, I'm only
relating my experiences. And in my experience nitrogen can be deadly even without being pressurize and without
"suffocating" you. And yes I know that air is 78% nitrogen.

Nor am I an expert on the subject either, but with similar time in the
field (26 years) before going back to college, but I stress that was
nearly 20 years ago.

"My Guess" which is all I can do from here, is there may have been
some traces of something other than N2 there. BUT as has been
mentioned, loss of consciousness is quite rapid in a pure N2
atmosphere. It's not usually instantaneous but quick. More like 5
to10 seconds which is about the time it takes for the process of
"removing" O2 from the blood in the lungs and the oxygen depleted
blood reaching the brain. However from my training (which was a long
time ago) the convulsions appear very soon, or almost as soon as the
loss of consciousness.

"My understanding" which could be flawed both by time and changes in
industry understanding since I left:

Our lungs work based on the "partial pressure" of O2 in the air. When
the partial pressure of O2 in the air is normal the lungs pass O2 into
the blood where the red blood cells bind the molecules of Oxygen and
carry it to where it is needed. Just about the first location being
the brain.
When the partial pressure drops below a given value (I've forgotten
the actual value) the lungs cease to pass the O2 into the blood
stream. Only a slight decrease from that point will cause the process
to reverse. Two things will cause this. remove the O2 from the
atmosphere and/or reduce the atmospheric pressure. This is the reason
why breathing pure O2 at high altitudes using a canula doesn't work.
You need the pressure of a mask.

OTOH blood that has had the O2 removed has an effect on the brain that
is quite different than Oxygen starved blood. It really messes with
the brain and does so quickly which accounts for the rapid onset of
convulsions. It's my understanding that the onset of brain damage is
also much faster as the blood is actually scavenging Oxygen from those
cells. The whole system has been thrown into reverse. The drop in O2
in the brain causes the neurons to start firing randomly which of
course results in convulsions.

That makes getting not just fresh air, but pure O2, to the patient as
quickly as possible, *essential* as you only have a small fraction of
the time normally available that you would have in the case of
asphyxiation. Even when pure O2 is applied you not only have to get
the amount of O2 in the blood up to normal, but it has to re oxygenate
areas that have less than normal amounts of O2, maybe way less. That
means the lungs themselves are going to be using up the O2 for a short
time before there is enough to supply the brain and the lungs are
going to be dealing with Oxygen starved blood for some time.

The brain is supposed to be capable of lasting up to 3 minutes or
possibly more without fresh air, the time available in this case may
be less than a minute. So, it is possible that this was a case of
inhaling pure N2 which would have given him just about time enough to
put the mask back in place before going down. The convulsions would
have probably started about the time he hit the floor.

Again, though, I stress it has been a long time since I had to deal
with this stuff on a day-to-day basis and I have not kept up with it
since then. "I think" which means I don't really know for sure, but
the treatment is pure O2 as quickly as possible and then like CO
poisoning, you keep the patient still as movement can make the
situation worse if done before the blood has been completely re
oxygenate.

Roger Halstead (K8RI & ARRL life member)
(N833R, S# CD-2 Worlds oldest Debonair)
www.rogerhalstead.com


I think this thread has drifted way to far off topic. For anyone else still interested go here Go here if you'd like
to read up on confined space requirements.
http://www.osha.gov/pls/oshaweb/owad...able=STANDARDS

Joe Schneider
8437R



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