Date: Tue, 15 Feb 2005 09:47:21 -0500
Reply-To: "Suzanne M. Kupiec, MPH, CSP" <kupiecsm**At_Symbol_Here**UMDNJ.EDU>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: "Suzanne M. Kupiec, MPH, CSP" <kupiecsm**At_Symbol_Here**UMDNJ.EDU>
Subject: Re: when do you have to work in a hood?
Comments: cc: gsteehle**At_Symbol_Here**ROANOKE.EDU
In-Reply-To: <3B6BF6B31FCC3240A651B450ADF774A801397696**At_Symbol_Here**EXCHANGE1.academi>

Gail -

You do not have to measure exposure.  The OSHA Regulation, 29 CFR
1910.1450, Occupational Exposure to Hazardous Chemicals in Laboratories,
says, in the (non-mandatory) Appendix A, E.1.n:

"As a rule of thumb, use a hood or other local ventilation device when
working with any appreciably volatile substance with a TLV of less than
50ppm."  (I personally use 100ppm as the threshold for requiring that work
be done under the hood, even if the substance is not particularly volatile.)

Under this criteria, hexane would have to be used in the hood, whereas
ethyl acetate would not.  However, on the bench-top, you do not have good
control over how vapors move and the location of ignition sources.  Since
ethyl acetate has a flashpoint of -4 degrees C,  I would recommend that it
be used under a hood where vapors are continually removed, and because you
can limit the ignition sources.

(As a side note, odor can be used as another criteria for use in the
hood.  Even if the chemical is relatively non-hazardous but it has an
obnoxious smell, it has to be used in the hood.)

Do you have a chemical hygiene plan in place?  What does it say?  The goal
should be that the lab should be safe for the population considered the
most sensitive, pregnant females.


(Just my opinion, and it does not represent anyone else's opinion here at

Suzanne M. Kupiec, MPH, CSP
Senior Industrial Hygienist (and Lab Safety Specialist)
Environmental & Occupational Health & Safety Services
Univ. of Medicine & Dentistry of New Jersey
675 Hoes Lane, Tr. #1
Piscataway, NJ 08854
(732) 235-4058/ fax - (732) 235-5270

At 04:00 PM 2/14/2005, you wrote:
>I am at a small college and trying to give good advice to researchers
>about when work needs to be done in the hood.  The chemicals we work
>with typically have PEL or similar values listed on the MSDS but, of
>course, I have no meter to measure those levels in the lab.  Lacking
>such hard data, is there any reasonable standard I can offer bench
>chemists to help them decide when work needs to move to the hood?  I
>currently have researchers doing column chromatography with hexanes and
>ethyl acetate on the bench outside the hood.  When I express concerns,
>the response starts "when I was in grad school, we did it this way . .
>."  I did lots of things in grad school that I couldn't defend then, let
>alone now.  Without the ability to measure (or estimate?) levels, I
>can't do much to change behavior.

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