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Xenos
Harmless
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Registered: 29-8-2002
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Fume Hood Design
Ok, this might be a really bad idea, or it may be a good idea. I was thinking about eventually, one day, making a fume hood. Comercial fume hoods cost
more than a used car, and used ones are not much cheeper, so I was thinking about making my own. Online, there are plenty of metal and glass
suppliers. There are also companies who sell fume hood filters for $300. I was thinking about this too, and wondering if activated aquarium charcoal
couldnt be used. Perhaps there is something im missing when it comes to carbon filters. Or, perhaps i could use a resperator filter, i have a few of
them laying around. So, basically, i was planning on making a small metal fume hood, with safety glass and corrosion resistant metal and of course a
filter. Now is the time to either improve on my idea, or tell me that id kill myself if i tried to do this. 
[Edited on 5-9-2005 by chemoleo]
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Rhadon
Hazard to Others
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Vacuum cleaner fume hood
I don't know if this is applicable for you, but I made myself a fumehood out of an old vacuum cleaner. If you place the device outside of your room
and lead the tube through a narrow gap of a small window, not much of the aspirated gases will be able to enter your room again. Placing the opening
of the tube above the opening of your reaction flask will work reliably.
In order to test its abilities, I placed the opening of the vacuum cleaner tube above an erlenmeyer flask that was filled with ammonia. Since none of
the NH3 gas seemed to be able to escape the suction, I heated the ammonia until it boiled, and the air was still clean of NH3
gas!
Obviously, this method doesn't work for highly corrosive vapour or vapour that forms corrosive compounds with water - or your vacuum cleaner won't
work for long. If you have to do, though, you could fill the bag which usually catches the dust with a substance that neutralizes the corrosive vapour
or with active charcoal.
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bangandow
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I imagine you could make mone pretty similar to the flowhood here (Click the link on the left that says "TEKS" and then click on the flowhood link). To adapt it to chemistry instead of mycology, just replace
the hepa filter with a carbon scrubber or filter of your choice and mount the blower inside the box so it creates negative pressure and draws air in
through the scrubber. You could also adopt metal instead of wood if need be. You can vent the box out to wherever the hell you want with ducting... I
dunno, sorry it's late and I'm rambling. 
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Anarchist
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why not just use scuba diving gear with an oxygen tank. You will have to modify it slightly maybe add some more chemical resistant materials, but I
think it would work though i'm not sure how much scuba gear costs exactly.
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Organikum
resurrected
Posts: 2329
Registered: 12-10-2002
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final solution: bilge fan
The final solution for an affordable explosion proof fan for a fume hood was found in the so called "bilge fans" for ships. They are quite cheap,
relieable and exactly whats needed.
The hood itself may be made of some glass and whats handy. Plastic foil and some wire or just strings, thick cardboard soaked in limewater is
perfect. It´s not for eternity....
But the bilge fan is a "must be", no discussion on substituting it. (ok, the blower from a oil-burner central heating unit - but this is quite
loud....)
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Xenos
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I put my plans into action a while ago, and built the fume hood. It took about 3 days and about $100 in supplies, but miraculosly it works! Its
basically a wooden box with no front (still working on that). Its lined with white PVC like plastic and the seams are caulked. There is a baffle and a
cheap bathroom fan in the center. Also a light, and an outlet. Im also working on water and gas connections  . Point being: it acually works and it prevents my garage from smelling like nitric acid or chlorine for weeks.
The ASPCA never liked Shrodinger, but they never knew he was a theroretical physicist.
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Organikum
resurrected
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a few days of use
and your bathroom fan will have gone the way of corrosion.
Please aquire a bilge fan then. Your next substitute might decide to go the way of electrostatic and combustion.
But of course it´s your life and your eyes and hands.
And no, I am for sure not one of those "don´t try this at home" guys.
Sorry if it sounds as I would be one.
ORG
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Hermes_Trismegistus
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Fumehood substitute
reprinted w/out permission from LabDad
Arguing on the internet is like running in the special olympics; even if you win: you\'re still retarded.
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Chris Owen
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The best hood I've ever used was a homemade 12' plywood one with 2 - 10" squirrel cage blowers, from a junk yard. The blowers lasted
about 5 years before falling apart. The wood was coated with polyurethane boat resin. I was dissolving a lot of gold scrap with hot aqua regia.
One can also use a two piece sliding window from Home Depot mounted on a plywood box.
Chris Owen
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Jupiter
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building hood
I am planning to built an hood using a toilette aspirator, but I am worried 
for the electrical motor that may be in conctat with flamable vapour. May be dangerous? - Possible solutions?
Using a brushless motor? Mounting the motor far away from inlet of aspiration?
Can someone give me a little help?
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garage chemist
chemical wizard
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When the motor is running, the flammable vapors are way too dilute to be ignited. There's really no need to worry about this. You can use your
toilette aspirator without problems.
The only thing to worry about are corrosive vapors (especially HCl), which attack your motor even at very low concentrations. Its lifespan will be
considerably shortened.
I think there was another thread about fume hoods?
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12AX7
Post Harlot
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Hm, aren't bathroom fans shaded-pole motors? (Looks like a flat slab of laminated iron with a coil on one end, the round armature in a loop and
several thick copper loops around the core.) They are sparkless, so as long as that's what motor is in it and the switch is away from fumes,
you're safe.
Tim
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Magpie
lab constructor
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My fume hood blower with discharge plenum is installed and tested. It moves a lot of air! I haven't installed the suction piping yet but have
the 8" PVC fittings on order.
I concur with garage chemist that it should not be necessary to have an explosion proof blower as I intend that escaping solvent vapors will be highly
diluted. My air-flow will be 400-500 cfm. I checked with a specialist with a large supplier of lab fume hoods and he agreed with this premise.
Caveat: this is a matter of judgement and I cannot guarantee there will never, under any circumstances, be a fire in my duct system. As insurance I
am considering a CO2 deluge system for my ducting such as I have seen in the hoods of restaurants.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Fleaker
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A good filter material would be a column of activated charcoal especially for absorption of volatile organic fumes.
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Magpie
lab constructor
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Yes Fleaker I agree that activated charcoal is good for adsorbing organic vapors. I should make a provision in my suction piping for an option to add
a charcoal adsorber and/or a filter. One must be a little carfeful with charcoal, however, as it in itself can be fuel for a fire. This occured at
work one time when there was too much organic material in the airstream and the heat of adsorbtion resulted in a charcoal fire.
My 1st choice is to have neither charcoal, filter, or scrubber in my fume hood ducting and see if I can get by without them. All of these increase
pressure drop (thus cutting flow) and present other problems. Now if one is intending to release mercaptans then I agree that charcoal would be in
order.
[Edited on 3-8-2005 by Magpie]
The single most important condition for a successful synthesis is good mixing - Nicodem
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Magpie
lab constructor
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This is just a progress report on my fume hood project. I have finally finished the blower system with rigid 8" (20 cm)ducting. The suction
opening is located 42" (1.1m) above my lab bench. When I hold a dangle-o-meter tissue 8" (20 cm) below the suction port it pulls it
straight up.
I am now working on the design of the hood itself. This will be portable. My main problem will be to keep down its weight.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Eclectic
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Bilge Blowers!
I just discovered these. $18-32, 12v.
For venting gasoline fumes from engine compartments.
http://www.boatus.com/boattech/bilgblo.htm
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Magpie
lab constructor
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Ah yes bilge blowers. I do remember now that they have been previously suggested on this forum.
At first glance they appear to be just the ticket, i.e., designed to vent gasoline fumes, corrosion resistant, and cheap.
There is no performance (fan curve) presented but this is likely available from the manufacturer. The largest unit (240 cfm) is about half the
capacity of my 9" blower but I'm sure larger ones are available.
My blower runs off 120 VAC. 12V battery management could be a hassle. Also there is no mention of noise. This is usually dependent on RPM. If I
remember correctly from my boating days the bilge blower had a bit of a whine to it. But any blower is going to make some noise.
I think bilge blowers are well worth looking into. 
The single most important condition for a successful synthesis is good mixing - Nicodem
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Eclectic
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They seem to be only available up to 240 CFM and 4" duct. But I suspect that they can be voltage throttled, and have a safety advantage in that
you could set up a power supply with a car,marine, or even gel-cell battery and a charger and not lose ventilation during a power outage.
You probably could hack a computer UPS to provide blower power and uninteruptable AC line voltage for lighting.
240 CFM at 12V, 4-5 amps! Less than 60 watts!
[Edited on 4-9-2005 by Eclectic]
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Magpie
lab constructor
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For more ideas on building a fume hood I suggest doing a search on "bilge" or even "fume hood." One good thread is:
http://www.sciencemadness.org/talk/viewthread.php?tid=208
Too bad these threads get separated over time but that is what happens when people don't search first before posting.
By Chemoleo: Thanks, it's merged now. Any other threads dealing with it?
[Edited on 5-9-2005 by chemoleo]
The single most important condition for a successful synthesis is good mixing - Nicodem
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Eclectic
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Actually I did search (and read). I thought I was making a novel and usefull suggestion regarding the uninteruptable power supply. More sutable for
smaller hoods, chemical and solvent storage, dark rooms, low budgets. Wasn't trying to steal your thunder...
I'll post more info on the DetMar 4" blower when I actually have one to experiment on and dissect.
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Magpie
lab constructor
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Chemoleo - thanks for merging the threads. I think this is an important subject and well worth the effort.
Eclectic: I was not saying that you did not search! I was referring to Jupiter. But that was his first post so we can't be too hard on him.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Magpie
lab constructor
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static electricity question
When I was assembling my 8" PVC suction piping for my fume hood blower I notice how quickly the pipe developed a static electricity charge. Then
I remembered that the high velocity venturi blowers (i.e., Coppus, etc) have a grounding strap for those made of fiberglass. As I don't want any
static discharges in my ducting system I thought I'll need a grounding strap also. But when I turned on the blower and ran it for a few minutes
there appeared to be no static buildup. The pipe is connected to the metal (grounded) blower by a Neoprene rubber boot (or sleeve) held in place with
radiator clamps. Is the static just being led to ground through the rubber boot to the blower? Or am I missing something here?
The single most important condition for a successful synthesis is good mixing - Nicodem
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neutrino
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I may be missing something here—why is a grounding piece made of fiberglass (an insulator)?
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Magpie
lab constructor
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Neutrino,
The venturi blower "horn" can be purchased in various materials, e.g., steel, fiberglass, etc. Those made of fiberglass come equipped with
a grounding strap (a copper wire) to lead off the static electricity.
The single most important condition for a successful synthesis is good mixing - Nicodem
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