Jay Young was kind enough to point out that page 34 of Volume 1 of Safety in Academic Chemistry Laboratories includes a good statement on the pros and cons of ductless fume hoods and suggests guidelines for their use in very specific situations. An additional reply that I would like to share with the list is below. - Ralph Date: Mon, 02 May 2005 13:15:15 -0700 From: "John J. Seabury"
Organization: Lawrence Berkeley National Laboratory Subject: Ductless Fume Hoods Ralph - good afternoon. I understand from one of my associates, Larry McLouth, that you posted an inquiry to the ACS Div.of Chemical Health and Safety listserve about ductless fume hoods. He suggested that I might wish to respond, as I oversee contaminant control ventilation issues for our facility. By way of introduction, Larry and I work at Lawrence Berkeley National Laboratory (Berkeley, CA) in the Environment, Health and Safety Division. LBNL is a US Department of Energy research laboratory that is operated by the University of California. Although we are located on UC Berkeley land and many of our researchers have joint faculty appointments with UCB, we are a separate organization. We have on the order of 4800 employees, about half researchers (professional and student) and the balance support staff. To directly respond to your question, we do not have any specific policies addressing "ductless" fume hoods. We do have the benefit of being notified of all fume hood purchases, and have an excellent working relationship with our researchers that would mean that if a researcher felt the need for a hood, they might consult us in the project development stage. If a project progressed beyond that state to one where formal design was begun, we have strict project management procedures in place to involve us in the design. So, in short, rather than to rely upon a policy, we feel that chances are pretty good that we might be informed of a need so that we could evaluate the best solution. EH&S's position (which will become codified when I revise our Laboratory Ventilation Management Plan, I'm hoping to do this sometime in the next several months) is that there are too many limitations to the use of "ductless" fume hoods to recommend them for general use. I suspect that you've already figured that out as well. Charcoal adsorbents have limited adsorptive capability both in terms of the chemicals that can be adsorbed as well as service life; there is no way to correctly determine effectiveness of control; most HEPA-filtered ductless hoods are not set up to be penetration-tested, and the like. Our feeling is that if the operation cannot be safely conducted on an open benchtop, then a "ductless" hood cannot be used for contaminant control, and a conventional ducted fume hood is required. "Ductless" hoods may supplement, but cannot replace, a conventional (exhausted) hood, and even then the possible uses are limited. One operation that I do recall that we authorized "ductless" hoods to be used was for researchers used prepackaged "Hach" water quality test kits. These tests can be safely conducted on open benchtop, but the researcher felt that he wanted to provide the teaching messageto his students about always using hoods. He feld that the use of the "ductless" hoods would provide additional containment airflow but would not be the primary control against hazard - the non-volatile chemicals and unit packaging of the kits provided that. So we concured. Our annual assessment consists of verifying that the user has complied with the use restrictions (No Hazardous Chemicals) posted on the hood. Regarding your examples, it's hard for me to envision how someone pouring a few ml of acetone would not be able to safely do so on an open benchtop, so for this operation a "ductless" hood might be appropriate. In research, though, things change daily, and the temptation to use the hood for other operations for which it would not be appropriate (knowingly or inadvertently) would be present. Pouring is relatively innocuous, but if same volume of acetone was vaporized at elevated temperature, or dispensed through an air supplied gun (such as an airbrush, for example spraying thin layer chromatography plates), then it could be a problem. I hope this helps. Best wishes. John Seabury -- John Seabury, PE, CIH Senior Professional Environment, Health & Safety Division Lawrence Berkeley National Laboratory 510-486-6547 (voice) 510-486-4845 (fax)
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