From: Bruce Van Scoy <vanscoybruce**At_Symbol_Here**FRONTIER.COM>
Subject: Re: [DCHAS-L] Benchtop Methylene Chloride Use in Undergraduate OChem labs
Date: Tue, 18 Nov 2014 19:15:37 -0500
Reply-To: DCHAS-L <DCHAS-L**At_Symbol_Here**MED.CORNELL.EDU>
Message-ID: 009201d0038d$f55c3fc0$e014bf40$**At_Symbol_Here**
In-Reply-To <073439EC-C2A5-4F7E-BD07-1DB775124C54**At_Symbol_Here**>

Maybe the initial question should be to ask the chemist making the
determination, specifically to define how the determination is being made
and to what criteria.
If the determination is made upon limiting the maximum extraction quantity
to not have a STEL, IDLH, etc., exposure scenario in case of an accident, I
would be impressed and want to hire any graduate of that program!
However, if the determination is made based upon the chemists reliance upon
odor threshold, designed ventilation system performance, instead of standard
IH quantification, as used ventilation evaluation, etc., then we not only
have a great deal of training/education to complete, but job security as
P.S. The job security comment is due to the rapid turnover in undergraduate
organic chemical labs and not meant to be detrimental in any way.

-----Original Message-----
From: DCHAS-L Discussion List [mailto:dchas-l**At_Symbol_Here**MED.CORNELL.EDU] On Behalf Of
Stuart, Ralph
Sent: Tuesday, November 18, 2014 6:46 AM
Subject: Re: [DCHAS-L] Benchtop Methylene Chloride Use in Undergraduate
OChem labs

>As many OChem labs lack adequate fume hoods, many colleges do these
>extractions at the bench,

My first response doesn't answer the overall question directly, but is about
a question that I've been wondering about. What do chemists mean when they
say "adequate fume hoods". Is it a question of the number available for the
number of work stations desired? Or is it a question of fume hood

One reason I ask is that I've seen peer reviewed papers that direct someone
trying to replicate the procedure in an "efficient fume hood" for safety
reasons. I'm not clear what that means; from a safety point of view, to
fulfill their safety function, fume hoods should capture fugitive chemical
vapors released and efficiency isn't part of the safety picture. I'd like to
understand the chemists' perspective on fume hoods better.

To more directly answer the question, the industrial hygiene approach to the
overall question is that measuring the concentration of methylene chloride
in the air during the work and comparing it to an appropriate exposure limit
(take your pick from ) should help
determine whether the lab facility is up to work being conducted in it. When
you look at that link, you'll see why that is a trick answer...

- Ralph

Ralph Stuart, CIH, CCHO
Chemical Hygiene Officer
Keene State College


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