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Hello Mac,<br><br>If the hood is isolated in a small lab 60 might work, otherwise I would stick with 100.<br><br>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.<br><br>Vince<br><br><br>NanoFab Manager<br>National Institute of Standards<br>Center for Nanoscale Science and Technology <br>100 Bureau Drive<br>Gaithersburg, MD 20899<br><br>301-975-2886<br> <br><br><br><br>Sent with Good (www.good.com)<br><br>
<br>
-----Original Message-----<br>
<b>From: </b>Mac Hathaway [<a href="mailto:hathaway@cns.fas.harvard.edu">hathaway@cns.fas.harvard.edu</a>]<br>
<b>Sent: </b>Wednesday, April 11, 2012 10:10 AM Eastern Standard Time<br>
<b>To: </b>labnetwork@mtl.mit.edu<br>
<b>Subject: </b>Re: [labnetwork] Face Velocity for Wet benches/Fume hoods?<br>
<br>
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.<br>
<br>
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?)<br>
<br>
Thanks again.<br>
<br>
<br>
Mac Hathaway<br>
Harvard Center for Nanoscale Systems<br>
<br>
<br>
<br>
<br>
<br>
On 4/6/2012 10:11 AM, Joe Morgan wrote:
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<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Mac,<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">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.<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Best,
Joe<o:p></o:p></span></p>
<p class="MsoNormal"><span
style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
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<p class="MsoNormal"><b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext">From:</span></b><span
style="font-size:10.0pt;font-family:"Tahoma","sans-serif";color:windowtext">
<a class="moz-txt-link-abbreviated" href="mailto:labnetwork-bounces@mtl.mit.edu">labnetwork-bounces@mtl.mit.edu</a>
[<a class="moz-txt-link-freetext" href="mailto:labnetwork-bounces@mtl.mit.edu">mailto:labnetwork-bounces@mtl.mit.edu</a>] <b>On Behalf Of
</b>Mac Hathaway<br>
<b>Sent:</b> Thursday, April 05, 2012 3:09 PM<br>
<b>To:</b> Lab Network (<a class="moz-txt-link-abbreviated" href="mailto:labnetwork@mtl.mit.edu">labnetwork@mtl.mit.edu</a>)<br>
<b>Subject:</b> [labnetwork] Face Velocity for Wet
benches/Fume hoods?<o:p></o:p></span></p>
</div>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">Hey all,<br>
<br>
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?<br>
<br>
The topic came up today in the context of energy savings, lab
make-up air, and this sort of thing...<br>
<br>
<br>
Thanks,<br>
<br>
Mac Hathaway<br>
Harvard Center for Nanoscale Systems<o:p></o:p></p>
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