News From the Hood, Volume 1, March 2002
FEBRUARY Issue No.3 2 0 0 4

Brought to you by The Applications Team at Lawrence Berkeley National Laboratory.

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Technical Questions:

Geoffrey C. Bell
gcbell@lbl.gov


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The Berkeley Hood
Applications Team
LBNL
EETD

Fumehood PictureLaboratory fume hoods are highly energy-intensive pieces of equipment found across a spectrum of industries and in educational labs. Each hood uses as much energy as a home, and we estimate that existing fume hoods use up to half a billion dollars of energy each year. The Berkeley Hood project is working towards the commercialization of an alternative that will cut energy use by 50% or more, while improving Fumehood Picture safety through improved containment of dangerous materials in the hood and reducing the size and first costs of facility HVAC systems thanks to lower overall airflow. This newsletter keeps readers abreast of new developments in research being conducted in this exciting area by the Lawrence Berkeley National Laboratory (LBNL) Applications Team.


We’ve Expanded: 6-foot Berkeley Hoods Come of Age.  

We have developed a new generation of Berkeley Hoods with 6-foot (nominal) openings.  The prototype hood has successfully passed tracer-gas containment tests (see below).


Pushing the Envelope: 
The Berkeley Hood Shows Robust Performance

We have completed an initial study of the performance “envelope” of the push-pull Berkeley Hood, to better understand its ability to maintain containment across a range of operating conditions. Over 100 test runs were performed on a four-foot hood with different amounts of supply airflow.  The results were very favorable, with no failures in normal operating modes. Among the specific findings:

  • Containment is maintained over a broad range of supply plenum airflows.
  • Containment is maintained at very low supply plenum “push-rates.”
  • The optimum combined push-rate seems to be at approximately 60 to 70 percent of total exhaust flow.
  • Consistent containment was achieved with combined push-rates between 35 and 85 percent of total exhaust flow.


Meeting the Standard

Industry leaders are recognizing the limitations of face velocity as an indicator of hood containment and, thus, safety.  ANSI, who promulgated the face velocity standard for many years, now strongly recommends against its sole use as a performance test.  Their newly adopted Laboratory Ventilation standard Z9.5-2003 (developed with the American Industrial Hygiene Association, AIHA) requires using the more meaningful tracer-gas testing, which verifies containment.  Experts have found that many hoods pass a face velocity test but fail these more robust containment tests.  Worker safety is not well served by relying on face velocity measurements as the sole performance indicator.

LBNL requested an interpretation of the new standard in the context of the push-pull Berkeley Hood.  Following are excerpts from ANSI/AIHA’s interpretation:

"Prior to the 1980s, face velocity and visual smoke observations were used as the major indicators of hood performance.  Recent studies have indicated that face velocity alone may not be predictive of adequate hood performance.”

"[I]t seems that your specific design of hood may not lend itself well to evaluation solely by face velocity tests.”

“Clearly, your design is not typical, and if effective containment can be demonstrated at a lower face velocity than that provided in the guidance, it would appear that this particular hood was in conformance with this aspect of ANSI/AIHA Z9.5-2003.”

“The current document [ANSI/AIHA Z9.5] indicates that containment, and not face velocity is the primary performance criteria.”


New Projects Underway

The Fume Hood development team began a major set of new activities under sponsorship of the California Energy Commission’s Public Interest Energy Research (PIER) Program.  This work will bring the Berkeley Hood closer to commercialization by conducting several demonstrations of the 6-foot hood and performing containment tests per ASHRAE 110-1995.  The project will also include interacting with CAL-OSHA, which must provide variances for the proposed industrial demonstrations.  Side-by-side tests with a conventional hood will also be performed and reported. The test methods and protocol will be developed in concert with industry experts and will include standard as well as non-standard tests (e.g. with operator motion).


Technology Transfer Award

On November 21, 2003, Lawrence Berkeley National Laboratory Director Charles Shank presented 16 Lab employees with Technology Transfer Awards. The honor recognizes inventors and their technologies that bring benefit to society. This year’s list includes the Berkeley Hood. For more information, see: http://www.lbl.gov/today/2003/Nov/24-Mon/TTD-awards.html