Fume hood in HP Labs

[VERNIG.PETER@FORUM.VA.GOV]

{Original Msg: 'Fume hood in HP Labs' from <radsafe@romulus.ehs.uiuc.edu>
{
{Question: Do you use a fume hood as part of your health physics operations?
{ Is the fume hood part of your "health physics" lab or do you use a fume hood i
{n another facility?
{ Reason: For years our operation has had the use of our own fume hoods because
{we took over lab space previously occupied by a research group that needed the
{fume hoods. Now we are moving to a new facility without a fume hood and need ju
{stification for spending the money to install a hood.
{  New question: How do you as a health physicist feel about the need for a fume
{ hood as part of your own health physics facility? If you can find the time to
{respond send the response to me at  milwicz@princeton.edu    Thanks
 
 
My strong feeling is that you probably do not need a fume hood in an HP
lab.  Fume hoods are designed and intended to remove hazardous fumes or
gases from the vicinity of someone working with a process that uses or
generates such gases or fumes.  You should ask yourself, does anything
we do generate a radioactive gas or aerosol?  The most common radioactive
gases are Tritium gas, krypton-85, and xenon-133.  Xe-133 is used in
nuclear medicine imaging.  Will you handle any of them?  The next most
common need for respiratory protection is from sodium iodides incorpor-
ating any radioactive isotope of iodine.  Iodination, the process of 
tagging or labeling somthing with radioactive iodine frequently leads to
some generation of iodine gas.  Anytime an iodide [iodine 1- ion] is
in the prescence of hydronium [hydrogen 1+ ion /acid ion] iodine gas is
formed and the gas leaves the solution.
 
Many research labs have fume hoods and they are often used inappropriately.
They give the research personnel a warm, fuzzy, protected feeling.  All the
bad karma from the chemicals in the hood is swept up the hood with the air
flow.  Generally, organic solvents should be used in fume hoods, to 
minimize
exposure to their vapor.  Any any reaction that generates a gas that is,
toxic, irritating, flammable, etc. should be carried out in a fume hood.
Many research labs put use of radioactive  materials in fume hoods.
I'd say half of the labs here do.  None of them need to.  We do no 
iodinations, all of the researchers using I-125 buy proteins and amino
acids already labeled.  I used to work for U.C. Berkeley and as a consult-
ant to NASA's Ames REsearch Center, Mt. View California and many of their
fume hoods exhausted through HEPA filters.
 
Now ask yourself what will a HEPA filter do for a gaseous effluent?
Nothing!  But people can be soothed by saying that a HEPA is 99.98%
efficient.  What that means is they trap that percentate of PARTICLES
of a specific size.  Generally, though there are exceptions, HEPA
filters are irrelevant to fume hood exhausts.  But many facilities have
installed them.
 
Sorry, you touched one of my hot buttons.  But ask yourself?  What is the
hazard I am trying to protect against?  In this case it is a gas, aerosol,
or dispersible powder that is also a hazard.  If you do LSC you might 
look at the MSDS for the cocktale.  I would recommend you purchase a
low toxicity form of LSC cocktale, but all of them have aeromatic solvent
systems and none of that is good for you.  I would think a fume hood is 
over kill for that but some kind of local exhaust would be nice as the
stuff invariably has an unpleasant odor.
 
REgards, Peter G. Vernig, VA Medical Center, Denver,
vernig.peter@forum.va.gov
 
 
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