Cindy Ridenour wrote:
> I just wanted to add my $0.02 on the oxygen sensor issue.
>
> Someone made the comment that the O2 level needs to drop only a few % to be
> trouble. For those of us who live at altitude, this is a surprise. Here at
> 5000 feet, the atmospheric pressure is down 15-20% from sea level (and so is
> the partial pressure of O2 - the critical issue). It falls even more
> at higher elevations. People ski and climb at 13000 feet routinely in
> Colorado where the pressure is almost 50% of sea level and people live at 16000
> feet in other parts of the world. The result is that for altitudes of
> less than 1000 feet, if the %O2 has fallen from about 21% to 10%, that is
> the same as going to about 15000 feet. For a person in reasonable health,
> there is no danger or hazard for short (or even longer) exposures to check
> out the situation in the lab. If the %O2 is less than 10%, (The cryogen
> boil off has displaced more than half of the original air in the room.)
> this would present a hazardous situation for most people for more than a
> brief exposure. Additionally, an oxygen sensor would be more important
> as you go up in altitude since there is less oxygen that one could safely
> displace with cryogen boiloff.
>
> This does beg the question that without a monitor, you do not know the O2
> content of the air if you do have a ventilation failure and a quench or
> cryogen container failure simultaneously.
>
> Joseph Ford
>
> *****************
> Joseph J. Ford, Ph.D.
> joe.ford@nmr.varian.com
> Phone (970)493-7007 ext. 217
> ******************
--=+=+=+=+=+=+=+=+=+=+=+=+=+=+= Jim Breeyear Univ of Vermont Manager, Inst. Chemistry Dept. email: jbreeyea@zoo.uvm.edu Home Page: http://www.uvm.edu/~jbreeyea AOL Instant Messenger handle: CRITIAS1