We are installing a chemical fume hood, vented to outside, with a sink at
one end and sitting space to coverslip at opposite end away from sink. The
lip that is part of the hood, designed for air flow and keep sash from
smacking into bench top will be removed, it is in the way for solvent
dispensing and a flat, uniform surface (difficult to reach over for fine
fingertip tasks) and is of no consequence. Look for a hood opening (sash
that raises) where you can lift a 5 gal can into, if necessary. I put my
PMMA waste into a metal can of this size, and LEAVE IT inside a running
hood, to make sure there are no methacrylate monomer fumes. If you use
glass bottles to collect MMA waste, it polymerizes and explodes - this
happened next to me - so metal cans became a must. 
 Remember if you can smell it, you have exposure!  Same for formalin. I
have had two hoods with this design, and they are wonderful.

Labline is one being looked at, hoods that have carbon filters eventuall
get saturated with solvent fumes.  There are different styles and blowers,
contact their rep through Fisher, VWR, etc -  he will work with you on what
you want.  Some hoods have flammable storage cabinets underneath for
solvents, nice but take up sink/sitting space.  An 8 foot hood is a
delight, we go with 6 feet this time, liveable. 

Our hood will be used for multiple tasks:

Dispensing xylene, other solventsinto their containers for
processor/staining. 
Routine staining setup (rehydration/dehydration steps)
Bone decalcification, acid handling/dispensing
Coverslipping at end opposite sink 
Poly methylmethacrylate and glycol methacrylate technics for bone - making
up solutions, infiltration, embedding
EM plastic work
Handling tissues fixed with formalin (NBF), gluteraldehyde, osmium
tetroxide, and Spurrs or other epon plastic methods
Snap freezing tissues with liquid nitrogen cooled isopentane or hexanes

This hood is the mainstay of the lab, our home away from home.

methyl methacrylate monomer mixtures are nasty with carbon filter hoods,
when saturated, you probably will smell fumes and if that happens, your
filter needs to be changed, exposure to fumes must be avoided at all costs
- toxic to your motor sensory system.  I prefer NOT to change a used filter.  

I love downdraft hoods for coverslipping, but with all the other major
things we do, the chemical fume hood vented to outside is the only way to
guarantee safety. I find most histology labs have such a large volume of
volatile solvents, fixatives - the classic outside venting is a must, at
least in our case. 





Gayle Callis
MT,HT,HTL(ASCP)
Histopathology Supervisor
Veterinary Molecular Biology - Marsh Lab
Montana State University - Bozeman
19th and Lincoln St
Bozeman MT 59717-3610

406 994-6367
406 994-4303 (FAX)