[labnetwork] Face Velocity for Wet benches/Fume hoods?

[Luciani, Vincent]

Hello Mac,

If the hood is isolated in a small lab 60 might work, otherwise I would stick with 100.

At NIST our safety office uses the 100 CFM number and in my personal experience it seems to be a good number. If you want to go lower than that you need to take in consideration the surrounding area of the hoods and the typical variations in make-up air and exhaust flow. I have found that below 80 CFM fume containment can be compromised by adjacent hoods, hoods directly across (opposing) and fluctuation in static pressure of the cleanroom or lab. We have servo controlled dampers but these fluctuation do happen. 100 CFM seems to hold up against all this noise.

Vince


NanoFab Manager
National Institute of Standards
Center for Nanoscale Science and Technology
100 Bureau Drive
Gaithersburg, MD 20899

301-975-2886




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-----Original Message-----
From: Mac Hathaway [hathaway at cns.fas.harvard.edu<mailto:hathaway at cns.fas.harvard.edu>]
Sent: Wednesday, April 11, 2012 10:10 AM Eastern Standard Time
To: labnetwork at mtl.mit.edu
Subject: Re: [labnetwork] Face Velocity for Wet benches/Fume hoods?

Thanks to all for the helpful replies.  At CNS, we are using 100 fpm on our fume hoods and wetbenchs, per ANSI.  However, with the push for energy conservation, we're keeping our eyes open.

It is interesting to note that the possibility of 60 fpm appears to be bench-specific.  Has anyone tested their benches at this flow, successfully or not?  Was this in a clean room (with vertical air flow?)

Thanks again.


Mac Hathaway
Harvard Center for Nanoscale Systems





On 4/6/2012 10:11 AM, Joe Morgan wrote:
Mac,

See ANSI/AIHA Z9.5 for laboratory ventilation systems and worker health.  In the past 100 feet/per minute has been the golden rule.  However, for a number of years now fume hood manufacturers have created new designs that sometimes enable sash velocities as low as 60 feet/minute.  The hood must still pass testing and certification as defined by ASHRAE 110.  I’m not sure how wet process benches or laminar flow hoods fit into these standards.

Best, Joe

From: labnetwork-bounces at mtl.mit.edu<mailto:labnetwork-bounces at mtl.mit.edu> [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Mac Hathaway
Sent: Thursday, April 05, 2012 3:09 PM
To: Lab Network (labnetwork at mtl.mit.edu<mailto:labnetwork at mtl.mit.edu>)
Subject: [labnetwork] Face Velocity for Wet benches/Fume hoods?

Hey all,

What do folks currently consider satisfactory regarding the air-flow face velocity at their fume hoods and wet benches?  Do you have any ASHRAE/ANSI/SEMI-type standards or references that you draw on for this purpose?

The topic came up today in the context of energy savings, lab make-up air, and this sort of thing...


Thanks,

Mac Hathaway
Harvard Center for Nanoscale Systems

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