Light-induced sneezing and Argon effects

[DANIEL ROBERT HOLDSWORTH]

In article <326BC80B.24A3 at cs.uwp.edu>, Paul D Boyer PhD <boyer at cs.uwp.edu>
writes:

<snip>

:Another question is whether there are any side effects from breathing
:Argon gas.  This is a case of industrial exposure, where the tank warns
:that inhalation should be followed by removal to fresh air, and if not
:breathing, give artificial respiration.  Sounds a bit threatening, but I
:also know some manufacturers are a bit overzealous in their warnings. 
:Anyone have any comments?

This is to do with the breathing control system in your brain. There are two
systems which operate to control breathing, but of these the one operating
from the carotid sinuses is by far the most important. This senses the amount 
of carbon dioxide (CO2) in the blood; the more CO2 present the greater the 
breathing rate induced.

Air contains a low level of CO2. Industrial Argon contains nothing but argon,
hence no CO2 and no oxygen, either. It is quite possible to breath pure argon
or pure nitrogen briefly with no ill effects, but the effect of a leak of 
argon into a room will be to displace some air.

Note that the leak is replacing air (oxygen/nitrogen mix with low CO2) with
argon, which contains no oxygen and NO CARBON DIOXIDE.

That means that your blood CO2 level will fall (as will your blood oxygen
level)
which will act to slow your breathing rate. This further reduces blood
oxygen,
which leads to unconciousness.

Once the victim is unconcious in the same environment where the leak was, 
they are likely to die without intervention. Indeed, the loos of conciousness
is particularly dangerous where bottled gases are concerned, since gas released
from a cylinder will be colder than ambient temperature, and will tend to sink
(Boyle's law) thus the person, when they collapse, will fall into a greater
concentration of the inert gas.

So, if you're using argon gas, vent to an extractor fan, and keep the place
well ventilated. It's not poisonous, just inert.

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Dan Holdsworth, drh92 at aber.ac.uk
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