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 wrote:
>
> From: eugene_ngai**At_Symbol_Here**comcast.net
> Subject: Tragic Asphyxiation
>
> A lot of discussion recently on Liquid Nitrogen safety. Here is a tragic example of asphyxiation
>
> http://www.koreaherald.com/view.php?ud 180904000834
>
> Eugene Ngai
> Chemically Speaking LLC
>
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