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Matt:<br>
<br>
I think that it is common, but probably not universal, to drill a
hole in a duct and then to use a hot-wire anemometer to create a
velocity profile of the exhaust duct in use.<br>
<br>
I've attached a photo of one of our exhaust lines coming out of a
HBr cabinet.<br>
<br>
In the upper portion of this photo, you'll see a cheap little red
plastic plug that was used for this type of velocity profiling.
Nothing special ... and if the exhaust were off, which it never is,
the little red plug is barely held in the duct.<br>
<br>
Also, you can also see in this photo the 1/4" diameter hole that is
used for the return of our extraction-type gas detector. If you are
using or plan to use extraction-style gas detectors, you may have a
hole that could be used for velocity profiling with a small-diameter
anemometer. Note: if this photo gets rotated, the duct should be
running vertically with the red plug above the white plastic
detector return line.<br>
<br>
<img class="moz-attached-image" shrinktofit="true"
src="cid:part1.08090604.06010500@stanford.edu"><br>
<br>
Note: not all of our exhausts have been for this purpose. Wet
benches, for example, are typically balanced based on face velocity
measurements rather than total exhaust flow.<br>
<br>
Good luck,<br>
<br>
John<br>
<br>
<div class="moz-cite-prefix">On 12/17/2014 10:48 AM, Matthieu
Nannini, Dr. wrote:<br>
</div>
<blockquote
cite="mid:2D63C893-A74A-4A9B-9A40-0E0A430D7A13@mcgill.ca"
type="cite">
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Colleagues,
<div><br>
</div>
<div>First, thank you for the handful of information about bending
coax tubing. </div>
<div><br>
</div>
<div>Now, facilities services here at McGill want to assess our
ventilation/exhaust capacity. To measure exhaust they want to
drill 3/8'' holes into each duct leading to a tool, take a
reading and plug it back. They show me the plugs they want to
use and I’m not convinced at all especially for the gas cabinet
exhaust. They don’t want to un-connect the tool and measure
directly as they want to make its resistance is taken into
account. </div>
<div><br>
</div>
<div>Any body has experience regarding that matter ?</div>
<div><br>
</div>
<div>Thanks in advance</div>
<div><br>
</div>
<div>Matthieu</div>
<br>
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<span class="Apple-style-span" style="border-collapse:
separate; color: rgb(0, 0, 0); font-family: Helvetica;
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<div style="word-wrap: break-word; -webkit-nbsp-mode:
space; -webkit-line-break: after-white-space; ">
-----------------------------------
<div>Matthieu Nannini<br>
McGill Nanotools Microfab<br>
Manager<br>
t: 514 398 3310<br>
c: 514 758 3311<br>
f: 514 398 8434<br>
<a moz-do-not-send="true"
href="http://mnm.physics.mcgill.ca/">http://mnm.physics.mcgill.ca/</a><br>
------------------------------------</div>
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