Chemical Fume Hood Use Guidelines

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The protection provided by laboratory fume hoods is dependent upon two important factors:

Proper Use

  • Continually monitor air being drawn into the hood by attaching a kim wipe or light-weight strip of paper to the bottom of the sash.
  • Operate the hood at the proper sash height indicated by the arrow attached on the side of the hood. This sash height should be approximately twelve inches from the bottom for optimum protection when conducting operations in the hood. A low sash height maximizes air velocity through the hood face and may provide additional protection from unexpected splashes or chemical reactions.
  • Avoid using the hood for storage of bottles and equipment, especially along the back wall. Any apparatus that must be housed within the hood should fit completely inside the hood. Elevate the apparatus on blocks (at least 2 inches tall) to allow air to flow freely around and beneath.
  • Manipulations within the hood should be performed at least 6 inches inside the face of the hood or as far towards the back of the hood as possible. This minimizes the possibility of contaminants escaping from the hood.
  • Fully close the hood sash and turn off the fan (if possible) when the hood is not in use. The fan should remain on if volatile materials are being temporarily stored in the hood.
  • Things which cause air turbulence across the face of the hood such as fans, air conditioning units, or excessive movement should be avoided.
  • Exhaust hoods do not provide adequate protection for all operations involving toxic materials. A higher level of containment should be used for procedures where minor contamination can be serious. If you are in doubt about the level of containment needed for your operation, ask your Principal Investigator or contact the Environmental Health and Safety Office (EHSO) Chemical Hygiene Officer at x65180.

Maintenance of Adequate Airflow

EHSO conducts annual surveys of fume hoods to ensure adequate airflow is maintained through the hood face. Face velocities should be between 80 and 120 feet per minute (fpm) with a sash height of 12 inches. Hoods that operate below 80 fpm are considered inadequate and should not be used for protection from toxic or volatile materials.

If your hood is inoperable, please call EHSO for an inspection.

Phone: 933-3300
Email: keni@hawaii.edu