From: Alan Hall <oldeddoc**At_Symbol_Here**GMAIL.COM>
Subject: Re: [DCHAS-L] Tragic Asphyxiation
Date: Wed, 3 Oct 2018 07:45:53 -0500
Reply-To: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU>
Message-ID: CALDugaY7i=8Rq+_ydRZw+ukcGOEY90Gt4ve2s1titfBQTLqFNg**At_Symbol_Here**
In-Reply-To <000c01d45b05$e43d1740$acb745c0$**At_Symbol_Here**>

Et al and Monona,

My medical toxicology 2 cents worth. An autopsy, even with a medical examiner and the types of lab toxicologists avvailable (which I am not) might not confirm the cause of death as exposure to either a simple or sysemic asphyxiant. I spent a whole year wandering around all over and lecturing to such folks about why you can't just assign the cause of death in fire smoke fatalities based only on a post-mortem CO level of 30% or greater, when at least 50% of such victims have died of cyanide poisoning (preventable with specific antidotes if the paramedics get there soon enough and have them available and know how use them use them).

Monona, your are quite rright about the time when you are still conscious but couldn;t help yourselft. In the Air Forece in the old days when I was a Reserve Flight Surgeon, they talked about the time of "useful consciousness" and then a period on consciousness when you could not. So we went into the altidtde chamber to a simulated altitude on 40,000 feet MSL. Being younger and even more foolish then, I agreed to do the hypoxia demonstration. Took off my face mask and respirator. Supposedly, you can't do more than 30 seconds in these conditions. I made it to a minute+, and then the inside safety instructor asked me if I needed my mask back on. I said yes, and just looked down at it my hand and was not able to move. At a minute 45 seconds, he put it on me and several breaths later wiiht 20 cm H2O PEEP (you have to work to breath out, and let the respirator blow up your lungs for you), I became as good as I am now. Air Foce uniform pants are quite blue, and my fingernails were darker bluet han that. I now believe in the "period of useful consciousness". Pure hypoxia isn't all that unpleasant, but it's certainly deadly if continured too long. .

Old school: I was always led from the front. If you can't be smart, be lucky.

AlanH. Hall, MD
Medical Toxicologist
Major, USAFR, MC, FS (Hon.Ret.)
Senior Advisor, Forensic Science
Weatherford College
Weatherford, TX

On Wed, Oct 3, 2018 at 6:33 AM Eugene Ngai <eugene_ngai**At_Symbol_Here**> wrote:
Does it really matter how they died? CO2 does have the effect you mentioned,
only, an autopsy would tell us what happened. In this case it was an
accidental discharge of CO2
that killed them. This is not an isolated case. A women sitting on a toilet
at a MacDonalds in Florida was asphyxiated since the liquid CO2 fill line
leaked. The key issue for me is that CO2 actually poisons a O2 detector
making it useless.

I was an expert witness on a case where liquid Argon was illegally loaded
below deck on a ship, the foreman and two of his crew were
that tragic case. CO2 since it's heavier than air can do the same very
easily. The medical effect is longer term exposure

-----Original Message-----
From: ACS Division of Chemical Health and Safety <DCHAS-L**At_Symbol_Here**PRINCETON.EDU> On
Behalf Of Osprey, James
Sent: Tuesday, October 2, 2018 7:31 PM
Subject: Re: [DCHAS-L] Tragic Asphyxiation

I don't doubt the lethality of carbon dioxide at elevated concentrations but
I take issue with the describing CO2 as an asphyxiant. Unlike nitrogen which
functions as a displacer of oxygen, CO2 at elevated partial pressure has a
direct effect on human physiology. Concentration in excess of 10% v/v are
immediately dangerous to life. I recall some authorities reporting pretty
near instantaneous incapacity (possibly due to heart failure) at 20% v/v In
brewing/baking industries where operators have leant into vats/dough bins
and been unable to assist themselves. (I would add that in these last
incidents the concentrations were estimated post mortem).

However I can report that in my student days, whilst making home brewed beer
and leaning on the lid of the brew bin I was exposed to a puff of
fermentation gas which I can best describe as an explosion in my nasal
passages like being kicked in the face with a violent recoil. That was a
learning moment.

Post graduation I developed a range of IR analyzers, one of which was used
in saturation diving. At depth, the gas mix in the bell is heliox and the
CO2 concentration is strictly monitored to maintain a very low ppm.

At face value one might assume partial pressure should not exceed 500 Pa.
However the risk of stratification is very much higher at the extreme
pressures (especially as balance is predominately helium) and alarm action
levels may be set at much lower levels.

Perhaps someone can advise the physiological pathways that elevated partial
pressure of CO2 adversely influences the body, even when the oxygen partial
pressure is maintained at normal levels.

James Osprey C Phys

Novatech Analytical Solutions Inc.
+1 514 378 9076

Sent from my iPhone

> On Oct 2, 2018, at 5:59 PM, DCHAS Membership Chair <membership**At_Symbol_Here**DCHAS.ORG>
> From: eugene_ngai**At_Symbol_Here** <eugene_ngai**At_Symbol_Here**>
> Subject: Tragic Asphyxiation
> A lot of discussion recently on Liquid Nitrogen safety. Here is a
> tragic example of asphyxiation
> Eugene Ngai
> Chemically Speaking LLC
> ---
> For more information about the DCHAS-L e-mail list, contact the
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