“New chemical fume hoods will not be purchased and installed without with the approval of WFSM EHS and Engineering. New hoods will be purchased that meet the design and operation requirements in ANSI Z9.5-1992 and will be tested in accordance with ANSI/ASHRAE 110 before use. New hoods will be added to the WFSM EH&S Annual Certification program after initial certification.”
The chemical fume hood is one of the primary safety devices in the laboratory ensuring an adequate level of protection from the possible harmful affects of chemicals. A well-designed hood, when properly installed and maintained, can offer a substantial degree of protection to the user, provided that it is used appropriately and its limitations are understood. Good Work Practices:
- Always check the airflow rate on the alarm to verify that the hood is working properly before beginning any work in the hood. If the hood is not equipped with an alarm, tape a small strip of Kimwipe on the sash. This will be drawn in when the hood is operating normally and serve as a visual warning to the user when the hood is not functioning properly as the Kimwipe will hang straight down. If the hood is not operating properly, or at all, close the sash and call WFSM Engineering at 716-4351 to arrange for repairs.
- When working with chemicals, the airflow rate in the hood shall be at least 100 linear feet per minute at the working height of the sash.
- In order to maintain the proper airflow velocity, hood sashes should never be opened beyond the marking provided by the yellow certification tape while work is being performed.
- Mark a line with tape 6 inches behind the sash and keep all chemicals and equipment behind that line during experiments. This will help to keep materials from escaping the hood when disturbances like air currents from people walking past the hood et cetera, interfere with airflow at the face of the hood.
- Perform work in a shallow tray if possible. If the hood does not have a recessed work area, minor spills will be contained in the tray or will serve to minimize spillage out onto the lab floor.
- Keep the sash glass clean. Never obstruct you view with paper, notices, decals et cetera.
- Keep the air foil clear. Never hang notes et cetera over the vents in the hood.
- Only a minimal amount of equipment storage is allowed in fume hoods. Excessive storage blocks air passage through the hood and results in air turbulence, which allows contaminants to escape. If large equipment must be placed in the hood, put it on blocks to raise it approximately 2 inches above the surface so that air may pass beneath it.
- No storage of chemicals is allowed in the fume hood.
- A conventional fume hood must not be used for perchloric acid. Perchloric acid vapors can settle on ductwork, resulting in the deposition of perchlorate crystals. Perchlorates can accumulate on surfaces and have been known to detonate on contact. Specialized perchloric acid hoods, made of stainless steel and equipped with a washdown system must be used for such work.
- A fume hood should not be used for waste disposal. It is a violation of environmental regulations to evaporate chemicals in a fume hood.
- When working with highly hazardous substances needing more containment than a fume hood offers, consider using a glove box.