mattrod9523
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How to Make a Fume Hood
I wanted to buy a fume hood, but the prices are crazy!!
I decided that it was probably best to make it myself, but I don't know where to start! Anybody have an idea on what material to use, and how to do
it? I think Jor has one, maybe he could help.
[Edited on 19-2-2009 by mattrod9523]
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Globey
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Seem to remember a great fume hood'esque idea I read about, where the vapors are channeled post U-Trap, into a sink. The water helps to dissolve/wash
the gasses, and the U-trap helps to ensure no "back-burp".
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panziandi
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hey mattrod... there are a few threads on home built fume hoods with designs, peoples photos, maths behind airflows, materials & coatings, fans,
costs etc on this board already. May I suggest you read them and ask a more specific question on one of those boards? Lots of info here already - good
luck building one and post some pictures!
Edit: spelling and re-wording
[Edited on 19-2-2009 by panziandi]
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chemrox
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First, try a little patience. I just passed on three that were for sale on ebay sold singly for about $300 each. I'm sorry I hesitated! Second if
you don't see something for sale that meets your needs You can certainly build one. Especially if you're good at wiring and plumbing. Keep in mind
one important fact; nearly all constant speed fan motors are induction types. This means they are explosion proof or sparkless at any rate. You can
spend a lot on acid resistant motors or install them so they're easy to replace. If you work the air flow right you won't be replacing motors or
ducting very often anyway. Before you build your own hood think about the rest of the lab buildout and see if the effort required matches your
priorities.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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Sauron
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My advice is, if you can't afford a new hood, buy a second hand one. LOTS of those not only on eBay but LabX and the used lab eqyuipment places like
SurplusLab.com (who may be now operating as Waters Edge something.)
Sic gorgeamus a los subjectatus nunc.
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Sedit
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"Before you build your own hood think about the rest of the lab buildout and see if the effort required matches your priorities."
I agree there are many things for the amature that can be done outside instead of a hood.
If the hood is the number one safety defense then chances are it should be done elseware.
Knowledge is useless to useless people...
"I see a lot of patterns in our behavior as a nation that parallel a lot of other historical processes. The fall of Rome, the fall of Germany — the
fall of the ruling country, the people who think they can do whatever they want without anybody else's consent. I've seen this story
before."~Maynard James Keenan
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Sauron
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In a residential environment, by which I mean suburbis, you need not only a hood but a good scrubber.
If you live out in the woods somewhere you can release what you want and no one will complain but the squirrels (and the wife and the kids.)
Otherwise you have your neighbors to consider and worry about. And I mean that on several levels.
You don't want to have them making trouble for you, and the best way to do that is to make sure you give them no reason to be offended.
Sic gorgeamus a los subjectatus nunc.
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Tinton
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Sauron is absolutely correct. You'd be surprised how quickly gases travel through yards.
Removing the stopper from a gas generator at the end of a reaction quickly makes the scent detectable to neighbors--especially when gases are driven
out during dilution of the reaction products.
People tend not to react well when their yard reeks of chlorine gas.
Scrubbing solutions are fun to design, and can be challenging sometimes(which is the fun of chemistry).
The reaction rate of the gas-absorbtion reaction has to exceed the rate of gas production minus the rate of gas usage.
It's useful to have some sort of gauge of the freshness of your scrubbing solution. Depending on the mass of the scrubbing system, I sometimes use a
balance to measure the gas absorbed, and calculate the reactant remaining.
I'd recommend calculating scrubbing necessities BEFORE you start your reaction.
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EmmisonJ
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i'm in the process of making one myself, thanks to all the valuable info on this board.
what material do i build it with?
depends on your demands, do you want it "explosion-proof" or not? if not, with the help of people here i made mine out of wood, silicone each corner
and soon will be layering a few coats of epoxy over it all to protect the wood and silicone. because i don't care about explosion-proof i actually
found a pre-assembled cabinet from a furniture store and modified it to fit my needs.
what design should i use?
the best thing to do is look at professional fume hoods, compare the differences in features and decide what it is that you need. personally that's
how i did it. then i followed magpie's dimensions regarding everything but the sash. i used two 2x4's on the back wall as support studs for plywood
pieces spaced out properly to serve as the baffles. i will do the sash last only because i will play around with different sash sizes to best fit the
blower i picked out. if the blower is lacking then i'll do a larger sash, if the blower is a bit much then i'll do a smaller sash. this is just what
seemed to be the easiest way to handle it for me b/c i know the blower is in the right ballpark but might be only slightly off in terms of cfm for my
area.
what about the blower?
this what really difficult for me to grasp, but with the help of these guys i learned a great deal or at least i learned enough to serve my purpose.
there are some posts on the board about this, mine is very recent and still on the first page.
but there are a lot of things to consider, some type of scrubber is something to consider, how you're going to run the ducting is also something to
consider. it's best to analyze each of these categories and draw up your ideas/needs then come back and ask specifics once you have a general
overview you want to iron out the details of. good luck
[Edited on 24-2-2009 by EmmisonJ]
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Aubrey
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Does anyone use a carbon filter with their fume hood? I've not seen one yet on this forum and was thinking of buying an inline fan / carbon filter
from a hydroponics shop, but then the question would be whether to put the carbon filter before or after the fan and how much this impedes airflow.
perhaps magpie can shed some light
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Magpie
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I really don't know much about hydroponics but suspect that their fans are meant to move a lot of air at a low pressure drop. That is, they may not
be suitable for ducting use.
On the charcoal adsorber placement I would want to know how the hydroponics folks use them. I suspect they are before the fan.
A word of caution: At one place I worked a fire started in the charcoal due to the heat of adsorption of some organics in the exhaust air.
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Aubrey
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Thanks for the reply, interestingly..
I just found this http://www.somhydro.co.uk/product.asp?pid=864
"This leads to only an 8% pressure loss and drag with fans as opposed to 20-30% with normal filters."
Interesting to note. I am happy to stump up a few extra quid for a 30% increase in suction if i am going to eliminate odour with a conventional carbon
filter.
AFAIK the carbon filters can be used in either configuration. I expect placing it after the fan is better giving more space inside the fume hood a la
commercial ductless fume hoods. (http://site.homegrown-hydroponics.com/modular-small-scrubber...)
[Edited on 11-4-2009 by Aubrey]
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AlChemicalLife
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in my opinion you should invest in a real lab fume hood, expesily if you are in a populated area cause u can get a duct less hood for around 3 1/2 -
4k (CHEAP!!!! Compared to spending 6k - 10+ k on a ducted hood) and i would take the risk for what i do,but i do use a homeade hood BUT I have buit
hoods before and had it tested by a profetional befor i used it. you can find hood cheap on ebay i saw one for 1K (AMAZINGLY CHEAP  ) and then the duct work and blower for around another 1/2 k - 1 1/2 k (this is
the one im buying ) and u also have to see what size u want. my lab cant fit one bigger then 60" (5FT) i use 48" hood  , dont forget safty is a very importent thing, if u cant aford to put safty first u
shouldnt be doing chemistry, they even have a arm hood witch is basicly a tube with a bowl type thing at the end that u use to suck out fumes,
http://www.coleparmer.com/Product/32_Wide_Enclosure_With_Fil... this is a ductless hood that dosnt need tube to go out side
this is a good hood that i want to get when i get about another 2k
http://www.coleparmer.com/Product/47_fiberglass_fume_hood_wi...
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AlChemicalLife
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in the sentence "i would take the risk for what i do" i ment wouldnt not would
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