We have several lab design or renovation projects concurrently  
underway. All of the engineers and project managers involved are  
interested in the use of low flow fume hoods (i.e. face velocity of  
around 60 feet per minute) to help support their LEED ratings and are  
asking our advice about 1) whether such hoods are acceptable to the  
institution and 2) which model is best.

The first question is relatively easy to answer; if they perform in  
the ASHRAE containment test similarly to traditional hoods, then they  
are ok. Either type of hood requires significant user education for  
them to be used effectively.

The second question is proving more challenging because of the short  
history of the low flow installations we've been able to identify.  
We've found three models which seem to operate on different design  
strategies:
- Air Sentry hoods use automatically adjusting baffles at the rear of  
the hood and an aerodynamically designed hood entrance to protect the  
containment vortex as cross-drafts, etc. threaten to disrupt it.
- Labconco Xtreme hoods use perforated back baffles to avoid the  
development of the vortex and maintain laminar flow through the hood
- Hamilton Fisher Concept hoods appear to rely on well crafted hood  
entrances to maintain containment at 60 fpm
I have talked about the Air Sentry hoods with colleagues who've had  
them in place for three years and who report no unusual problems with  
them.

I wonder if other people have evaluated these various options and  
decided that one design approach was preferable to the others from the  
users' point of view. My primary interest is maintaining some level of  
uniformity on campus, since our hood users travel randomly from  
building to building and we already have significant confusion on  
campus as to the different operating procedures for different hoods  
because of motion detector protocols, high low switches, etc.

Thanks for any help on this question (which I know other campuses are  
asking as well).

- Ralph

Ralph Stuart, CIH
Environmental Safety Manager
University of Vermont
Environmental Safety Facility
667 Spear St. Burlington, VT  05405

rstuart**At_Symbol_Here**uvm.edu
fax: (802)656-8682

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