Hi Andy and Margaret!
I agree with Andy’s assessment that ASHRAE 110 is a better determiner of fume hood effectiveness than mere face velocity. Face velocity itself is not a DIRECT measurement of containment
since sash HEIGHT determines how many CFM a certain face velocity will move. Additionally, hood containment is not the only issue since a very low volume hood can cause a caustic or explosive environment
inside the hood even if no bad stuff gets out.
Below internet link examines more thoroughly such hood issues as mentioned above.
https://www.flowsciences.com/thefeasibilityoffumehoodcontainmentat40fpm/
Dr. Bob Haugen
Director of Product and Technology Development
Flow Sciences, Inc.
910 332 4878
From: ACS Division of Chemical Health and Safety [mailto:DCHAS-L**At_Symbol_Here**PRINCETON.EDU]
On Behalf Of Glode, Andy
Sent: Thursday, October 4, 2018 2:04 PM
To: DCHAS-L**At_Symbol_Here**PRINCETON.EDU
Subject: Re: [DCHAS-L] Annual Certification Parameters for Fume Hoods w/Face Velocity Reduced to 80 fpm...
In my opinion, the starting point has to be the ASHRAE 110 test, not a general range of acceptable face velocities. When we have reduced flow rates as a result of a building energy recommissioning
projects, we perform ASHRAE 110 tests for each affected hood. Once a hood passes the ASHRAE 110 test, we use the face velocity recorded during the successful ASHRAE 110 test as the baseline for future tests. Our acceptance criteria for hood face velocity for
periodic hood tests (at least annual) thereafter is no lower than 10% below the baseline and no greater than 20% above baseline, which is from the ANSI Z9.5 Laboratory Ventilation Standard.
I hope this helps.
Andy
Laboratory Safety Manager
Office of Environmental Health and Safety
University of New Hampshire
603-862-5038
Caution - External Email
Good morning,
For those of you who have worked with an industrial hygiene or engineering company involved with sustainability efforts which include adjusting laboratory ventilation, when you
have had fume hoods originally set to average 100 fpm face velocity reset to average 80 fpm face velocity, what was your 'fail' point when recertifying? (These are 'standard', not "high performance" fume hoods.)
The original ANSI standard considered any average values between 80-120 a "pass"; obviously while we'd prefer to never deviate downward, there is likely going to be some hood,
somewhere whose average reading is somewhat less than 80. I guess I can 'live with' a 5% deviation, but what about a 10%? If you accepted "70" for example, as passing, did you verify that with an ASHRAE 110 smoke test? Or ??? Yes, I know I can go back
to the consultants but I have a ton of respect for the technical and real-world knowledge of this group.
I realize that face velocity is just one measure of containment, that capture of vapors depends on a number of factors, etc, and our consultants did perform the ASHRAE 110 tests
on several hoods at 80 fpm before all similar ones were set to 80 fpm...I am looking for real-world advice dealing with what I have to work with...
--
Margaret A. Rakas, Ph.D..
Manager, Inventory & Regulatory Affairs
Clark Science Center
413-585-3877 (p)
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--- For more information about the DCHAS-L e-mail list, contact the Divisional membership chair at
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