Fume Hood Face Velocity
Is Face Velocity an Accurate Measure of Hood Performance?
Many reports, studies, and other research suggest that maintaining a specific face velocity does not guarantee that a fume hood will contain harmful chemical fumes. Factors other than the velocity at which air enters a fume hood opening are important in determining the fume hoods ability to contain. The following is a list of reports that support performance-based, fume hood containment tests over face velocity measurements.
For more information on these studies and the individuals and organizations that published them, click on the links below each quote. We would like to thank each author and organization for their hard work in helping to improve laboratory worker safety.
"The ability of the laboratory fume hood to capture and contain hazardous fumes and vapors is often equated to its face velocity. Although average face velocity and containment efficiency are related under ideal conditions, they are not the same."
ìFace velocity testing and maintaining a specific face velocity does not assure fume hood containment.î
Hitchings, D. T. P.E., C.I.H., "An Improved Laboratory Fume Hood Performance Test: Beyond Instantaneous Face Velocity." 1996
"If traditional face velocity testing alone were used to determine performance, more than half of the hoods exhibiting high leakage and, therefore, high exposure potential , would have been overlooked. This case study and evidence from several thousand additional ASHRAE 110 tests performed on other fume hoods show that face velocity alone is a very poor indicator of fume hood containment."
Hitchings, D. T. P.E., C.I.H.. "Using the ASHRAE 110 test as a TQM Tool to Improve Laboratory Fume Hood Performance." December 17, 1996
"Tests prescribed in the ANSI/ASHRAE 110 Method of Testing Performance of Laboratory Fume Hoods (ASHRAE 110) standard including low- and high-volume smoke tests, face velocity tests, and tracer gas containment tests indicated that many of the hoods did not meet industry consensus standards for containment (0.1 ppm), yet met industry recommended face velocity specifications (80-120 ft/min)."
Maupins, Karen. Hitchings, Dale T. "Reducing Employee Exposure Potential Using the ANSI/ASHRAE 110 Method of Testing Performance of Laboratory Fume Hoods as a Diagnostic Tool." AIHA Journal: Vol. 59, No. 2., pp. 133-138. Feb 1998.
"The results of the study indicate that average face velocity may not be a reliable indicator of hood performance as escape was detected at some hoods operating at face velocities between 80fpm and 150fpm. Conversely, satisfactory hood containment was found in some cases were hoods were operating at average face velocities less than 80fpm and greater than 150fpm. The study concludes that reliance on average face velocity as the sole criterion for acceptable hood performance is overly simplistic and potentially misleading."
Smith,T. (Exposure Control Technologies, Inc.). "Use of Average Face Velocity as an Indicator of Laboratory Hood Performance." 1999 American Industrial Hygiene Conference and Expo Abstracts #174. Last Updated on June 23, 1999
"Qualitative assessments with smoke under different working conditions indicated poor smoke capture and containment of 20 percent of the hoods with face velocities within the 85 to 130 ft/min range."
Volin, C.E., Joao, R.V.; Rieman, J.S.; Party E.; Gershey, E.L. "Fume Hood Performance: Face Velocity Variability Inconsistent Air Volume Systems." Applied Occupational and Environmental Hygiene. Vol. 13(9): pp. 656-662, 1998.
"Upon completion of this research, it became evident that current face velocity standards for rating hood performance are inadequate."
Woodrow, Lisa Michele. An Evaluation of Four Quantitative Laboratory Fume Hood Performance Test Methods. U.S. Govt. Printing Office: 1987-0-573-034/ 80,000, pp. 103. Nov 1987.
"No correlation between average face velocity and containment was observed."
Greenley, P.; Billings, C.; DiBerardinis, L.; Edwards, R.; Barkeley, W. "Containment Testing of Laboratory Hoods in the As-Used Condition. "Applied Occupational and Environmental Hygiene." Vol. 15(2): pp. 215. Feb 2000.
"Face Velocities established in the past by the fume hood industry may not necessarily be a direct indication of good containment. Tracer gas tests have proven this."
State of Wisconsin, Division of Facilities Development. "Fume Hood Performance Test and Life Cycle Cost Analysis for University of Wisconsin Milwaukee Chemistry Building Fume Hood Replacement Project Phase 2." DVD Project No. 98303. pp. 1. February 21,2000.
"Face velocity alone is inadequate to describe hood performance and is not more important than supply air distribution."
"This standard does not establish a standard for face velocity because of the importance of other parameters and the existance of an applicable performance test (ANSI/ASHRAE 110)."
American Industrial Hygiene Association (AIHA). ANSI/AIHA Z9.5-1992 American National Standard for Laboratory Ventilation. AIHA: Fairfax, VA. ISBN 0-932627-50-1. Page 13. 1993.
"Measurement of hood face velocity is a handy way to determine that design air flow rates are being maintained; however, it is not a direct measure of a hood's ability to provide containment in spite of the fact that regulatory and professional organizations specify average face velocity as an operating criterion."
DiBerdinis, L., First, M., Ivany, R. "Field Results of an In-Place, Quantitative Performance Test for Laboratory Fume Hoods." Applied Occupational and Environmental Hygiene, Vol. 6(3): pp. 227. March 1991.