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Date: Tue, 3 May 2005 09:44:37 -0400
Reply-To: Ralph Stuart <rstuart**At_Symbol_Here**uvm.edu>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: Ralph Stuart <rstuart**At_Symbol_Here**uvm.edu>
Subject: Ductless fume hood follow-up
Jay Young was kind enough to point out that page 34 of Volume 1 of
Safety in Academic Chemistry Laboratories includes a good statement
on the pros and cons of ductless fume hoods and suggests guidelines
for their use in very specific situations.
An additional reply that I would like to share with the list is below.
- Ralph
Date: Mon, 02 May 2005 13:15:15 -0700
From: "John J. Seabury"
Organization: Lawrence Berkeley National Laboratory
Subject: Ductless Fume Hoods
Ralph - good afternoon. I understand from one of my associates, Larry
McLouth, that you posted an inquiry to the ACS Div.of Chemical Health
and Safety listserve about ductless fume hoods. He suggested that I
might wish to respond, as I oversee contaminant control ventilation
issues for our facility.
By way of introduction, Larry and I work at Lawrence Berkeley
National Laboratory (Berkeley, CA) in the Environment, Health and
Safety Division. LBNL is a US Department of Energy research
laboratory that is operated by the University of California. Although
we are located on UC Berkeley land and many of our researchers have
joint faculty appointments with UCB, we are a separate organization.
We have on the order of 4800 employees, about half researchers
(professional and student) and the balance support staff.
To directly respond to your question, we do not have any specific
policies addressing "ductless" fume hoods. We do have the benefit of
being notified of all fume hood purchases, and have an excellent
working relationship with our researchers that would mean that if a
researcher felt the need for a hood, they might consult us in the
project development stage. If a project progressed beyond that state
to one where formal design was begun, we have strict project
management procedures in place to involve us in the design.
So, in short, rather than to rely upon a policy, we feel that chances
are pretty good that we might be informed of a need so that we could
evaluate the best solution. EH&S's position (which will become
codified when I revise our Laboratory Ventilation Management Plan,
I'm hoping to do this sometime in the next several months) is that
there are too many limitations to the use of "ductless" fume hoods to
recommend them for general use. I suspect that you've already figured
that out as well.
Charcoal adsorbents have limited adsorptive capability both in terms
of the chemicals that can be adsorbed as well as service life; there
is no way to correctly determine effectiveness of control; most
HEPA-filtered ductless hoods are not set up to be penetration-tested,
and the like. Our feeling is that if the operation cannot be safely
conducted on an open benchtop, then a "ductless" hood cannot be used
for contaminant control, and a conventional ducted fume hood is
required. "Ductless" hoods may supplement, but cannot replace, a
conventional (exhausted) hood, and even then the possible uses are
limited. One operation that I do recall that we authorized "ductless"
hoods to be used was for researchers used prepackaged "Hach" water
quality test kits. These tests can be safely conducted on open
benchtop, but the researcher felt that he wanted to provide the
teaching messageto his students about always using hoods. He feld
that the use of the "ductless" hoods would provide additional
containment airflow but would not be the primary control against
hazard - the non-volatile chemicals and unit packaging of the kits
provided that. So we concured. Our annual assessment consists of
verifying that the user has complied with the use restrictions (No
Hazardous Chemicals) posted on the hood.
Regarding your examples, it's hard for me to envision how someone
pouring a few ml of acetone would not be able to safely do so on an
open benchtop, so for this operation a "ductless" hood might be
appropriate. In research, though, things change daily, and the
temptation to use the hood for other operations for which it would
not be appropriate (knowingly or inadvertently) would be present.
Pouring is relatively innocuous, but if same volume of acetone was
vaporized at elevated temperature, or dispensed through an air
supplied gun (such as an airbrush, for example spraying thin layer
chromatography plates), then it could be a problem.
I hope this helps.
Best wishes.
John Seabury
--
John Seabury, PE, CIH
Senior Professional
Environment, Health & Safety Division
Lawrence Berkeley National Laboratory
510-486-6547 (voice)
510-486-4845 (fax)
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