Fume Hood Face Velocities

All fume hoods at University of Kentucky facilities should have face velocities between 80-150 feet per minute with the sash at a "working height" (approximately 12 inches). As a general rule, fume hoods should not be operated with the sash fully open and should have the sash closed when not being used. The office of Occupational Health and Safety (OH&S) will conduct a fume hood inspection and certification program for all fume hoods at the university. Fume hoods with face velocities within the 80-150 feet per minute range may be used without restriction and will be marked with a fume hood sticker showing face velocity at a height designated with an arrow.

Hoods Needing Repairs

Fume hoods with face velocities below 80 feet per minute or above 150 linear feet per minute must be marked with a sign indicating that the hood may not be used for chemical manipulations. A work order to repair these hoods should be processed as soon as possible. For UKMC this can be done online or by contacting the MCPPD at 3-6281. For Lexington Campus, contact your building administrator and/or operator. Once the hood has been repaired, OH&S will need to be contacted to reevaluate the hood’s performance.

Safe Work Practices for Laboratory Fume Hoods

When using a fume hood, one must remember that the hood does not provide absolute containment or absolute protection from the materials in the hood. However, for most exposures, a properly designed hood in a properly designed room can provide adequate protection if certain work practices are followed. The work practices listed below are recommended by the American Conference of Governmental Industrial Hygienists in their text: "Industrial Ventilation: A Manual of Recommended Practices."

A chemical fume hood cannot provide complete safety against all events that may occur in the hood, especially for toxic airborne contaminants with an exposure limit in the low part per billion range. For ordinary exposures, however, a properly designed hood in a properly ventilated room can provide adequate protection. Nevertheless, certain work practices are necessary in order for the hood to perform efficiently. The following work practices are required; more stringent practices may be necessary in some circumstances.

1. All operations that may generate air contaminants at levels above the exposure limit must be conducted inside a hood.

2. Keep all apparatus at least 6 inches back from the face of the hood. A stripe on the bench surface is a good reminder.

3. Do not put your head in the hood when contaminants are being generated.

4. Do not use the hood as a waste disposal mechanism except for very small quantities of volatile materials.

5. Excessive storage of chemicals or any apparatus in the hood will impair the performance of the chemical fume hood. Store flammable chemicals in an approved flammable storage safety cabinet. Store corrosive chemicals in a corrosive storage cabinet.

6. Be sure that the switch is in the "on" position whenever the hood is in use and test hood often for airflow (for example using a chemwipe).

7. Using hazardous solids (powders) in hood may not be appropriate.

8. Keep the slots in the hood baffle free of obstruction by apparatus or containers.

9. Minimize foot traffic past the face of the hood.

10. Keep laboratory doors and windows closed (exception: some laboratories are designed for the lab doors to be open).

11. Do not remove hood sash or panels except when necessary for apparatus set-up. Replace sash or panels before operating.

12. Do not place electrical receptacles or other spark sources inside the hood when flammable liquids or gases are present. No permanent electrical receptacles are permitted in the hood.

13. Use an appropriate barricade if there is a chance of explosion or eruption.

14. If hood sash is supposed to be partially closed for operation, the hood should be so labeled and the appropriate closure point clearly indicated.

15. Where perchloric acid is heated above ambient temperature, vapors may condense within the exhaust system to form explosive perchlorates. In such instances, specially designed fume hood exhaust systems must be utilized. These systems will have dedicated exhausts and a water washdown system, and may be used for perchloric acid digestions only.

16. All fume hoods should have spill protection lips (at the front of hood and for cup sinks located in the hood).