Demystify: 

> >We have found that a 3 foot fume hood for liquid waste collection (only) in teaching labs is a really excellent way of keeping vapors out of the lab (as they pour off) and not crowding the (second/working) fume hood that is used for procedures... It has helped us with compliance issues and training students on proper hazwaste handling procedures, so it's been worth it in our view.

I can see how those reasons make sense, particularly in a class lab. However, use of fume hoods for chemical storage also helps build the common lab habit of using fume hoods without a risk assessment of whether they are adequate to control the hazards of the chemistry being undertaken. In my mind, this habit explains the Wetterhahn mercury exposure we recently discussed and the fatal UCLA fire in 2008. In both of those events, fume hoods were not an appropriate control for the toxicity or fire hazards involved and the use of the hood seemed to end more complete consideration of other management steps (especially PPE) that might be needed for the risks involved.

Using a fume hood to collect the wastes you describe makes sense for a class setting because of the improved administrative controls (training and oversight) it provides, rather than the additional ventilation. I suspect that distinction is beyond scope of the safety education included in the classes you're considering. But in that context, 60 fpm face velocity _into_ the hood should work fine, as long as cross drafts from other activities in the lab don't disrupt the direction of that flow.

- Ralph

Ralph Stuart, CIH, CCHO
ralph**At_Symbol_Here**rstuartcih.org

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