[labnetwork] Reading ventilation/exhaust

[John Shott]

Matt:

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.

I've attached a photo of one of our exhaust lines coming out of a HBr 
cabinet.

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.

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.



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.

Good luck,

John

On 12/17/2014 10:48 AM, Matthieu Nannini, Dr. wrote:
> Colleagues,
>
> First, thank you for the handful of information about bending coax 
> tubing.
>
> 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.
>
> Any body has experience regarding that matter ?
>
> Thanks in advance
>
> Matthieu
>
> -----------------------------------
> Matthieu Nannini
> McGill Nanotools Microfab
> Manager
> t: 514 398 3310
> c: 514 758 3311
> f: 514 398 8434
> http://mnm.physics.mcgill.ca/
> ------------------------------------
>
>
>
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