Some chemical fume hoods are equipped with adjustable baffles located at the top and bottom of the hood's work area. Using a lever on the front of the hood, slots in the baffles can be adjusted in size to provide control over air flow within the hood.
Follow
Chemical Fume Hood Use Guidelines for general best practices. If your fume hood is equipped with adjustable baffles, select the best baffle position for the type of work being performed. The images at right illustrate baffle adjustment positions. The advantages they provide are described below:
- Position A provides the best performance for most fume hood uses. Contaminants typically mix quickly with air to form mixtures which have almost the same density as air. Position A, open at both top and bottom baffles, provides good flow in both the lower and upper parts of the hood work area.
- Position B gives the best containment when a large hot plate is used in the hood. Heat causes contaminants to rise. Narrowing the lower baffle and enlarging the top one allows more air to be exhausted
from the upper part of the work area.
- Position C is used for work involving heavy vapors such as halogenated solvents. Large volumes of very dense vapors tend to sink within the hood. Narrow the top baffle and enlarge the bottom one to increase the amount of air drawn through the lower work area.
Images and information source: Kewaunee Scientific Corporation, "Supreme Air Series Fume Hoods," P.O. Box 1842, Statesville, N.C., 28687-1842, page 69.
If you are a UCSD employee and have questions, contact an EH&S Research Assistance Program specialist.
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