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Date: Wed, 8 Apr 2009 14:50:25 -0400
Reply-To: List Moderator <ecgrants**At_Symbol_Here**UVM.EDU>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: List Moderator <ecgrants**At_Symbol_Here**UVM.EDU>
Subject: 3 more on class lab fume hoods
From: "R Alton Simpson (asimpson)"
Date: April 8, 2009 9:01:42 AM EDT (CA)
To: Ralph Stuart
Subject: FW: [DCHAS-L] Class lab fume hoods?
We still provide a small fume hood for each pair of students in
teaching labs; we also provide a few 4 to 6 foot hoods in the lab for
unusual tasks that need more room. These small hoods are ducted bench
top units that are quite adequate for the work, but use much less
space and air volume than a normal fume hood. The small hoods do pass
the ASHRAE 110 test.
Al
Alton Simpson, CHMM, NRCC-CHO
Director, Environmental Health and Safety
The University of Memphis
216 Browning Hall
Memphis, TN 38152-3340
(901) 678-4672 fax (901) 678-4673
http://ehs.memphis.edu
====
=0CFrom: ACTSNYC**At_Symbol_Here**cs.com
Date: April 8, 2009 9:10:18 AM EDT (CA)
To: ecgrants**At_Symbol_Here**uvm.edu
Subject: Re: [DCHAS-L] 12 Re: [DCHAS-L] Class lab fume hoods?
>In our Organic labs we currently have bench top hoods for each
student pair, as well as two larger hoods in each lab. We are having
one lab updated over the summer and installing island workbenches.
One hood will hang over each island and be accessible from all sides
so that two pairs can work under it. Then we will have 3 larger
hoods with sashes in the lab also, and one will be handicap accessible.
The only further comment I would have would be on this entry. This
type of canopy overhead hood violates the ACGIH industrial ventilation
principles and will not be effective for vapors and gases emitted by
evaporation or release at room temperature or below. Canopy overhead
hoods are only proper for very hot processes which will drive
emissions up into the hood's capture area which is only a few inches
from the face of the hood.
Emissions from the types of chemical procedures in most labs are only
effectively captured by enclosure such as the standard fume hood
provides.
Monona Rossol, M.S., M.F.A.,
industrial hygienist
Arts, Crafts &Theater Safety, Inc.
and
Safety Officer,
United Scenic Artist's, Local USA829
International Alliance of Theatrical Stage Employes (IATSE)
181 Thompson St., #23
New York NY 10012-2586 212/777-0062
artscraftstheatersafety.org
===
=0CFrom: "DAVID KATZ"
Date: April 8, 2009 10:40:59 AM EDT (CA)
Subject: Re: [DCHAS-L] 12 Re: [DCHAS-L] Class lab fume hoods?
Hi Ralph,
Some interesting responses to your inquiry. Here are some of my
experiences.
Currently, I work at Pima Community College in Tucson. I have been
here for 6 years. We have 3 chemistry labs with hoods along one long
side of the room. Two labs have 2 long 8 to 10 foot hoods with no
pull down sashes. There is a small 4 foot hood in the center that
does have a pull-down sash that we use for waste materials generated
during lab classes. The thrid lab has 5 6-foot hoods along with a
smaller hood like the other labs. The hoods have simply one-setting,
on or off.
To the best of my knowledge, they do not pull any make-up air from
outside to compensate for the negative pressure in the room. I have
no data on number of air exchanges per hour in the labs. Each hood has
at least one small sink in it along with gas jets. We generally do
not use the sinks, except for the lab reserved for organic
experiments, so they show the effects of non-use. We do use the gas
jets occasionally, but usually use hot plates or other electrical
sources for heating. These labs are over 25 years old. The hoods have
not been well maintained over the years and, after having hoods in one
lab non-operational for a week, I have recently insisted on starting a
monthly check of the hoods in addition to visual checks by facuilty
and our lab specialist. Overall, these have been adequate for most of
the work we do in our labs. I have been very instrumental in getting
our faculty to go to smaller scale experiments and eliminating those
experiments that produce too many fumes. The hoods are in dire need
of an upgrade, but I know our heating/air conditioning system could
not handle the load of more efficient hoods.
I keep asking about a new science building rather than replacement of
our hoods. Since the hoods should be on continuously, they should be
able to be powered down to a lower setting when the lab is not in use
or when we are lecturing in the lab. They should pull make-up air
from outside to reduce some of the strain of the heating/air
conditioning system.
In 1980, we designed new labs at the Community College of
Philadelphia. We wanted at least 6 5-foot hoods per lab with exhaust
canopies over each work area. The big problem was that the negative
pressure would he too high. We did end up with 6 hoods per room and
that was adequate for our classes, but did produce quite a bit of
negative pressure, even with make-up air being pulled into the hood
from outside. These hoods had two settings,"low and high". All the
hoods were equipped with a small sink, water, gas, compressed air, and
vacuum. The labs had about 8 air exchanges per hour. We were quite
pleased with the hood set-up in each lab.
I did work for 5 years at a small college where there was only one,
poorly functional hood in the lab along with poor ventilation. I had
to rethink all our experiments to adjust for those conditions.
Organic chem did not fare as well so we needed open doors and exhaust
fans. Thankfully, there was only one incident with an organic student
getting ill from fumes and that was settled without any legal
litigation. That college eventually built a new science building, but
that was after I left.
I cannot envision a chemistry lab without hoods. They are useful just
in speeding up water evaporation for some experiments. One of the
major factors to be considered is not just the number of hoods per
lab, but the experiments being performed in each lab. I would suggest
that the experiments be reviewed and updated for smaller scale and to
reduce fumes where possible. Plan the hoods for current and
anticipated student use, more hoods for organic and upper level labs,
less hoods for introductory labs. Remember to have a determination of
the number of air exchanges per lab per hour (no one mentioned that in
your compilation of answers) Portable hoods do serve a purpose, but
have very limited application - I only recommend them for something
such as an instrument room where we may be doing final preparation of
samples for instrumental analysis. I prefer students working in
groups of two, most of my colleagues allow groups of four (so some sit
around mainly observing rather than working). That will also affect
the need for hood space. Energy efficiency is also a major
consideration. Make sure that the company you work with has
experience with both academic and industrial lab construction. The
heating and air conditioning people should also be involved.
I hope my comments help.
David
_________________________________________________________________________
David A. Katz
Chemist, Educator, Expert Demonstrator, Science Communicator, and
Consultant
Programs and workshops for teachers, schools, museums, and the public
133 N. Desert Stream Dr. * Tucson, AZ 85745-2277 * USA
voice/fax: (520) 624-2207 * email: dakatz45**At_Symbol_Here**msn.com
Visit my web site: http://www.chymist.com
_________________________________________________________________________
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