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Offline zsinger

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Fume Hood
« on: March 10, 2014, 04:37:58 PM »
All,
I have picked up all the components for my fume hood including 2 110 CFM reverse fans, and a 3 cubic foot plexiglass box (given to me so can't complain).  Any ideas, warnings, past experience, as I have NO experience building a fume hood.  Im not all that handy, so an explanation of all steps would be great.  Thanks so much.  It will not let me include pictures for some reason…..maybe size?
            -Zack
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Offline AlphaScent

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Re: Fume Hood
« Reply #1 on: March 10, 2014, 05:18:23 PM »
Zack,

How are you going to ventilate it? Where are you going to put the motor?
If you're not part of the solution, then you're part of the precipitate

Offline zsinger

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Re: Fume Hood
« Reply #2 on: March 10, 2014, 05:39:23 PM »
ventilation with 2 110 CFM fans…..one mounted on the back bottom for heavy vapors, and one mounted on the top of the cube for light vapors.  I though this would take care of any/all vapors, as this fan sucks ALOT of air.

http://www.amazon.com/AC-Infinity-HS1238A-X-Standard-Cooling/dp/B009OWRMZ6/ref=sr_1_cc_1?s=aps&ie=UTF8&qid=1394487666&sr=1-1-catcorr&keywords=ac+infinity+110+cfm
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Offline Arkcon

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Re: Fume Hood
« Reply #3 on: March 10, 2014, 08:38:35 PM »
Hmmm ... a DIY fume hood.  Tricky.  OK some caveats.

The whole point of a fume hood is a system of baffles, they force fumes to travel a particular path.  Yes, you have two high power fans, but have you designed the back to guide the fumes, or will the just end up mixed by turbulence?  Compare the various hood designs on Wikipedia:  http://en.wikipedia.org/wiki/Fume_hood

How is the fan protected against hood vapors?  What's it made of, and are there exposed parts made of other things?  If the blades are metal, how will it resist corrosive fumes?  How will the plastic parts resist solvent fumes?  And how will the wiring, made of plastic over metal, handle both, in sequence?
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Offline zsinger

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Re: Fume Hood
« Reply #4 on: March 10, 2014, 09:23:01 PM »
Arkon,
THANK YOU!!!!! You may have just saved me from expending 10 worthless hours making a useless fume hood.

I am going to call the company and ask them how corrosive their parts are?…….either way, a 15 dollar part should it get shot.  The vacuum setup works, as I tried it with 5 lit cigarettes today.  I will update the forum as I continue to build!
             -Zack
"The answer is of zero significance if one cannot distinctly arrive at said place with an explanation"

Offline zsinger

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Re: Fume Hood
« Reply #5 on: March 10, 2014, 09:35:06 PM »
WOW!  Thank you again Ark……I did not realize that many solvents dissolve plexiglas.  Onto the PVC pipes idea…..anybody have a picture of a homebuilt one?
                -Zack
"The answer is of zero significance if one cannot distinctly arrive at said place with an explanation"

Online billnotgatez

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Re: Fume Hood
« Reply #6 on: March 10, 2014, 09:50:55 PM »
I used the Advanced search feature to check the Citizen Chemist forum and hits.
I took a quick look at some entries, but you might have better results looking more in depth or searching the whole forum. I bet if you did the GOOGLE you would get results also but you would have to sort out the good, bad and ugly.

http://www.chemicalforums.com/index.php?topic=60358.msg215899#msg215899
http://www.chemicalforums.com/index.php?topic=15832.0

Offline Arkcon

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Re: Fume Hood
« Reply #7 on: March 11, 2014, 03:26:30 AM »
Now see, this image shows a very simple hood.  Bot notice, it has a double back wall, that's how it forces fumes to take a certain path.  This model is molded, not fabricated.  I think you will need the help of someone who really understands aerodynamics.  And I don't know anyone on these boards who does. Still, you're already doing the smoke test, so you may be getting there.

A little while ago, I was doing some ignitions, that requires me to add conc. sulfuric and conc. nitric to an organic sample and heat until fumes cease.  I kept the sash all the way down, for everyone else's safety.  And fumes came right to the sash.  I asked "Shouldn't this hood be doing a better job?" and some one raised it to above midpoint, where it said it should be, and then the hood sucked the fumes right ou the back.  So, the aerodynamics of hoods isn't trivial.
Hey, I'm not judging.  I just like to shoot straight.  I'm a man of science.

Online billnotgatez

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Re: Fume Hood
« Reply #8 on: March 11, 2014, 11:10:35 PM »
I ran across this example of a home made fume hood.
I assume this home made fume hood would be vented so as to protect its user.
And, I also would assume would fail some of the fume hood suggestions previously made in this thread.
I am sure there are lots of other links out on the internet of better designs
« Last Edit: March 11, 2014, 11:27:24 PM by billnotgatez »

Offline zsinger

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Re: Fume Hood
« Reply #9 on: March 14, 2014, 06:11:43 PM »
I am going to build this fume hood with a few differences.  In addition to having the fan on top, I'm putting one on the back (I.E. right behind hotplate/stirrer/condenser)  Im having a hard time picking out a non-corrosive, totally inert material which can be bought in sheets and nailed into wood somewhat easily.  Any ideas?
                     -Zack
"The answer is of zero significance if one cannot distinctly arrive at said place with an explanation"

Online billnotgatez

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Re: Fume Hood
« Reply #10 on: March 15, 2014, 01:35:07 AM »
Doing some GOOGLE
http://www.escoglobal.com/resources/pdf/guide-fumehoods.pdf

I read this
Quote
A conventional fume hood must not be used for perchloric acid. Perchloric acid vapors can
settle on ductwork, resulting in the deposition of perchlorate crystals. Perchlorates can
accumulate on surfaces and have been known to detonate on contact, causing serious
injury to researchers and maintenance personnel. Specialized perchloric acid hoods, made
of stainless steel and equipped with a wash down system must be used for such work.


Offline zsinger

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Re: Fume Hood
« Reply #11 on: March 15, 2014, 07:48:26 PM »
Don't think I have ever done anything where perchloric acid (g) was given off, so I'm good there.  Im thinking polyethylene?  polypropylene?  I tried exposing the plexiglas to a copious amount of HCl (g) and it did NOT corrode quickly, leading me to further postulate that the fumes will be out before the "swelling" and "bubbling" i heave read about occur.
               -Zack
"The answer is of zero significance if one cannot distinctly arrive at said place with an explanation"

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