Date: Thu, 30 Aug 2007 09:54:35 -0700
Reply-To: Gordon Miller <miller22**At_Symbol_Here**LLNL.GOV>
Sender: DCHAS-L Discussion List <DCHAS-L**At_Symbol_Here**LIST.UVM.EDU>
From: Gordon Miller <miller22**At_Symbol_Here**LLNL.GOV>
Subject: Re: composite work

Ventilation combined with enclosure may work. As is well known, a 
high degree of enclosure can be used to minimize airflow and/or 
increase protection. It has already been pointed out that a lab hood 
on its own will not. Something like a glovebox with star-shaped 
cutouts in the ports instead of gloves, or a glovebox with a makeup 
air opening on one side and the exhaust takeoff on the other, or a 
plain old glovebox may be possibilities.

The comment about exotic, or at least unknown, air contaminants is 
true. Many commercial epoxies are blends of amines with known 
mechanical properties and that's about all known about them. They are 
also sensitizers rivaling the diisocyanates. If heat is applied, it 
will drive up vapor pressure. The curing reaction of epoxy is 
exothermic so there will be heating anyway.

If heating is strong enough to create thermal decomposition, this is 
another issue. I once recommended putting a carbon filter on an epoxy 
composite curing device for this reason. The carbon should be the 
kind found in multi-contaminant respirator cartridges because the 
range of compounds being sorbed could be large. Frequent changeout 
will be needed because the behavior of the unknown materials in the 
carbon is not predictable.

Respirators are a last resort, but maybe this is one task where 
they'll be needed anyway - especially if control ventilation is not 
the best. Airline or PAPR respirators with multi-contaminant 
cartridges (and frequent changeouts) are probably the way to go.

At 09:18 AM 8/29/2007, you wrote:
>As ever, please excuse the cross-postings.  I have a new researcher
>whose topic of interest is composites.  She does lay-up and manufacture
>of composites using various epoxies and resins.  She also tests
>composites with various liquids with which the composites might come in
>contact - jet fuel, de-icing liquids, etc.
>We are renovating lab space for her and she needs a place to "lay-up"
>various composite materials and vacuum bag the pieces to cure.  She has
>plans to do work on a full-scale car bumper and an unmanned vehicle of
>some sort.
>Currently, they work with small pieces in a (very small) fume hood and
>wear respirators when working outside of the hood.  I'm philosophically
>uncomfortable with folks routinely wearing respirators.  We can engineer
>out this hazard!
>A traditional fume hood probably won't work.  Backdraft won't allow for
>access all the way around the work piece.  We use down draft tables in
>anatomy teaching but will traditional down draft work in this situation
>with such a large surface area?
>Lemme know what ya'll think.
>Debbie M. Decker, Campus Chemical Safety Officer
>Environmental Health and Safety
>University of California, Davis
>1 Shields Ave.
>Davis, CA  95616
>(530)754-7964/(530)752-4527 (FAX)
>Co-Conspirator to Make the World A
>Better Place -- Visit and join the conspiracy
>University of California Industrial Hygiene and Safety
>UCIH&S website:

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