# Fume hoods plans ?



## Noxx

Hello guys,
I'm moving into a new house in a few months. Hopefully, I will be able to refine gold more often. And I'm planning to build a fume hood. Anyone got plans for this ? Harold gave me goods ideas on his previous posts.
I plan to use a big computer fan as an air exhaust. 
Oh, and the area where I will refine gold is 10'x12'
Thanks a lot.


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## jimdoc

Noxx,
You will have to set up the fan to create a draft or suction
to pull out the fumes, if you run the fumes through the fan it 
will fall apart in no time. 
I have some plans I found online when I find them, I will post them.
Jim


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## jimdoc

Here are some fume hood links that may help;

http://www.ehs.ufl.edu/lab/fumehood.htm#cert

http://www.psalab.com/catalog/PDF%20Catalogs/RESEARCH%20Hood%20Catalog%20120dpi.pdf

http://www.petedavis.net/MySite/DynPageView.aspx?pageid=45

I still have to check on my laptop for the one I was looking for.


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## Noxx

Hmmm... How can I pull out the fumes without making them go through the fan ?


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## jimdoc

I have pictures on my laptop, I will check that now
and post. Jim


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## jimdoc

Noxx,
Sorry, but I can't find the article with pictures on my
other computers. I will check to see if I printed it out.
I have a portable hard drive I saved a bunch of stuff
on when getting a virus out of my old P3 MS Millenium
machine, and now it isn't on there???? And I can't find 
it online anymore.
Basically it showed the blower fan behind the opening
at the top, so it was creating a draft or flow over the
opening and would draw the fumes up and out without
coming in contact with the fan or motor. It made sense
to me, because even if the fans are free, you don't want
them failing in the middle of a job with nitric fumes.
Jim


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## Noxx

jimdoc said:


> Basically it showed the blower fan behind the opening
> at the top, so it was creating a draft or flow over the
> opening and would draw the fumes up and out without
> coming in contact with the fan or motor. It made sense
> to me, because even if the fans are free, you don't want
> them failing in the middle of a job with nitric fumes.
> Jim



Thanks, thats what I taught...


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## rainmaker

This is how I did mine. Seems to work well, I'm still breathing.


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## Noxx

Yes mine will almost be the same...

But what kind of filter do you use ?

Thanks


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## Lou

This might be useful, a lot of the fellows over there have built fume hoods.

http://sciencemadness.org/talk/viewthread.php?tid=208&page=1


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## daveerf

Heya Knoxx , if no one answered your question of how to make the fumes go through the pvc pipe without going past the fan. Use a Y connection and put the fan on the end of the Y going off the main pipe. I'm including a crude picture to show what I mean.[/img]


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## aflacglobal

Hey, welcome back daveerf.
Long time no see. How's life treating you?


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## daveerf

Heya Aflac, thanks. Life is great and you? I've been super busy this summer and fall. That's why I haven't posted much.

Believe me, you might not want to see me post much because my usual brief replies tend to be a full novel. lol

Hope everyone else is doing good too. 

How did you like my drawing there? Picasso and Rembrandt have nothing to fear lmao


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## aflacglobal

Without the yellow letters it looks like a cave drawing of a water buffalo.  

Welcome back. Trust me some of my post read like novels to. :lol:


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## heirloomreplacement

Hello All
Just my two cents here

But I would think a great blower for a hood would be the type used in many marine applications>
They can be easy to tap into any kind of tubing from a side Y tube
they come in 3 and 4 inch sizes and have great CFM

You can find them cheap at any boaters world and on ebay
some would say the down side is they run 12 volts?
but easy fix is to just hook the leads to your Cell Power supply and walla>>>> you have airflow

One thing I can say is they are very efficiant> I use them often to ram air down the intake in cars.

anyway> that will be the way I try to get the fumes out, when i find room to have a hood set up

Jim


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## austexjwlry

Hello Noxx,

This is a temporary fume hood I made from a 70 gallon Rubbermaid container purchased at Wal-Mart for $13.

The blower is a little blue blower from Harbor Freight tools $39. on sale. I've mounted it with the motor side up. Just drilled and screwed through the inside of lid into the plastic blower housing. I've used duct tape to seal off most of the air flow from the top, leaving just a little air flow to help cool the motor.

The 4" black ribbed plastic water drain pipe comes in a 10' length at $4.
from home depot. I used a sleeve connecter ( about $2.) for connecting 2 pieces of the drain pipe together to attach the black plastic pipe to blower. Just squeezed it to roughly rectangular shape to fit opening in blower.predrilled holes and used machine screws to attach and silicon sealed.

I used a water closet (toilet) fitting to attach the drain pipe to plywood in window. A clothes dryer vent would work. I used silicon sealant and duct tape to seal everything.

I use the blower on low speed with more than enough suction to remove all the acid, sulphur dioxide, hydrogen, and oxygen etc. etc. while running 2, 13" x 9" casserole dish cells, using avg. of 40 alligator clips with up to 40 silver or gold plated items at a time.

I use 10ga solid single strand insulated wire which I strip the insulation from and solder 2" copper plated steel battery clamp type alligator clips to each end.

I use 2, 25 amp analog rectifiers, one for each cell.

I originally used a Y connector to keep the blower out of fume stream but the ribs in pipe or something caused backflow into container defeating purpose. I believe y connecter would work with 4" smooth wall pvc pipe. I have been using almost daily for 6 mths and if my motor ever burns out I'll upgrade to pvc.

This fume hood is not fire proof! You could possibly put a hotplate in a pyrex casserole sitting on fire bricks for hot work but I wouldn't recommend it.

This setup does a very good job of removing fumes created from cell use. This hood is sitting on a 4' x 2' white plastic table for reference as to size. Please refer to attached picture.

Wayne


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## Noxx

That's a great set-up :lol: 

Thanks for your explanation.


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## Smitty

That looks like a nice setup austex, but i'm concerned about the amount of weight on top of the container. It's starting to bend downwards a little or maybe it's the other additional equipment you have stored on top.


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## austexjwlry

Smitty,

Thanks for your concern, its probably justified! 

I only put the rectifer up there when I'm going to clean out the cells.

A water closet flange connector fits almost perfectly on the intake side of these little blue blowers allowing you to mount the motor away from the tuppaware with another flange connector on either side , back or top of the unit. Theres no reason to mount the motor on top. I like the 4" black drain pipe because its fairly flexable unlike 4" pvc.

I'd also suggest a hinged 1/8" clear plexiglass door to keep the family cat etc. out when not in use.

I've considered using a vertical or angled packed tower somewhat like used in a distillation tower except using a good sized limestone aggregate to still allow airflow and/or perhaps some scrubbers. Perhaps a inexpencive recirculating mist system like for irrigation of plants to help trap the fumes! I've tried blowing through wet polyester materials but it didn't work well. Perhaps a mist system on an a/c type filter would work?

Thanks for the interest!
Wayne


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## austexjwlry

Noxx,

Several years ago we had an ice skating rink at the northcross mall here in Austin that was remodeling and threw away all of the about 4' x 8' sheets of about 1/4" thick white plastic that it was made from. I was happily removing them from the commercial dumpster before the security guard made us put what we had back and leave. I should of asked for permission!

I think this type material would make a great fume hood as its thicker and seems to come in larger sizes than most plexiglass I've seen.

Wayne


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## ddrew

Greetings all,

I have added to a thread in the Safety Forum that I've been working with other members on a Fume Hood design. I just found this thread so I thought I'd link that other discussion and see if I can get any other ideas or input on my design. That thread is http://goldrefiningforum.com/phpBB3/viewtopic.php?p=15376#15376.

To summarize my design, I'm building a plywood cage (36" wide x 18" deep x 36" tall) with tempered plate glass sliding doors, and using a Telfon film applied to the inside surface. I found a 'Negative Air Machine' that produces 550 cfm of air suction through two prefilters and a cylindrical HEPA filter, and vents outside the hood. This machine is about the size of a rolling shop vac, and would have attach with an intake port on the bottom rear of the hood. I'm looking at using a refillable Carbon Prefilter (http://tinyurl.com/243jpq) that uses activated carbon and potassium permanganate as the filter media (http://tinyurl.com/yrusts) - see attached file for more info on this. I would use a pleated 1st stage prefilter to capture any airborne PM's. 

I was curious if anyone has any concerns about using this type of pre-filtration media with the various chemicals and fumes produced during refining processes described on this site. If a better pre-filtration media is suggested, please let me know and I'll be glad to consider it.

I also had questions about the make up air, and was undecided about bringing in fresh outside air, or simply recycling the exhaust air from the Negative Air Machine?

In regards to these Negative Air Machines, they are used in the asbestos abatement and carpet cleaning industries, and are found on craigslist or ebay quite frequently. The unit I found is a Dri-eaz DefendAir XL, but I was also looking at a CRSI 2000 (http://tinyurl.com/ys3bem) which is a much heavier duty unit. It has a exhaust capacity of 2,000 cfm, but is much heavier weight which would double it's cost in shipping weight (units are selling for $2-300 and freight is in that range too). I bought this DefendAir XL from a local carpet cleaning contractor that used to do mold abatement, and got this unit for $175 with local pickup. The difficulty is these HEPA filters are as expensive as the units, and that's why I want to capture as much in pre-filtration before going into the HEPA filter. 

I haven't purchased the pre-filtration filters yet, and would greatly appreciate any ideas, suggestions or other thoughts from the more senior 'forum fellows' that have worked with this topic. I'll be glad to make working drawings as soon as I get the design complete, and provide a copy to the forum library.

Thanks in advance for all input regarding this design.

Edited to try and fix URLs and attach file


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## Palladium

http://www.usplastic.com/catalog/product.asp?catalog%5Fname=USPlastic&category%5Fname=56&product%5Fid=14576


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## ddrew

Palladium said:


> http://www.usplastic.com/catalog/product.asp?catalog%5Fname=USPlastic&category%5Fname=56&product%5Fid=14576



Thanks Palladium, I appreciate the link. Any other comments on my fume hood ventilation plans? Have a great weekend, everyone!!


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## ddrew

Bump . . .

Buehler?? Anyone??


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## banjags

For a blower assembly... Would a blower and the box from a vehicle work... They move a lot of air and should be relatively easy to mount and adapt to a "custom" built fume hood.


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## grainsofgold

I tried constructing a fume hood like the diagram in the Hoke book . but I mounted the blower unit too high above where the fumes were being made and it did not produce enough of a draft to carry the fumes out. 

I was thinking about this recently and thought if you were to connect a blower via a step down connection into a small diameter pipe say 1/2 inch in diameter that is 2-3 feet long before it connects to a Y fitting - wouldn't this create a greater CFM and force the fumes up quicker to the outside vent? and of course bring the blower and the Y closer to the source of the fumes-

Art


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## Lou

It's all about the face velocity .

Keep in mind that improvising your own fume hood will probably make your work safer, but it won't make it anymore approved as it probably won't be code compliant.


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## goldsilverpro

If I remember right, you need about 100 cfm per square foot of opening.


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## Anonymous

Noxx:

I noticed your in Quebec so I thought I'd mention that the federal government often has equipment like fume hoods up for auction by sealed bid. (I understand they also have "Cash and Carry" sales too). When I was in Calgary several years ago, I checked out some of the auction items, including several fume hoods that they had at the time and while I didn't buy one, I did find out that they sold for under $10.00 each. They were about 6' tall by 5' wide and about 2' deep, with clear strips of some type of rubbery material in front, but I'd prefer plexiglass/lexan folding doors instead.

Check out the website here:
http://crownassets.pwgsc.gc.ca/main-e.cfm?sidenavcmd=contact
(If your close enough, the Ontario location might have more selection.) 

I recall some of the other scientific equipment, (professional microscopes, centrifuges, etc), and more industrial/mining related equipment they had, (on and off road wheeled and tracked vehicles and assorted machinery), that sold dirt cheap. Might be worth while checking out?


OGG.


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## Noxx

I will take a look, thanks.


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## Anonymous

the Y is sewer clean out it can be purchased at any HOME DEPOT, it produces a draft based on Bernoullis (spelling) research in the 1600's. It part of his work that describes low pressure lift or drafts (the theory of lift on an airplane wing).


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## Oz

Brav01,

That is the route I plan on taking as it does not involve the blower assembly being acid/fume resistant. It is very similar to the venturi effect.


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## grainsofgold

http://www.research.northwestern.edu/ors/labsafe/hoods/index.htm#Conventional%20hood


I found some good fume hood information and wanted to share it-


Grains of gold


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## jimdoc

Here is an Ebay link if anyone is in NY it may be worth checking out;
http://cgi.ebay.com/LABORATORY-FUME-HOODS-LOT-OF-4_W0QQitemZ330236580038QQihZ014QQcategoryZ26237QQssPageNameZWDVWQQrdZ1QQcmdZViewItem


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## Noxx

Guys,
I'm currently building my own, I should be able to post pics within a few days. 

Stay Tuned !


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## Oz

That’s great Noxx, I look forward to hearing what materials you chose and seeing your method of construction. This is something I need to do soon as well. It sounds as though you are beyond the planning stage but I have been thinking of using slate for mine, at least for the base and sides. Does anyone have any knowledge as to the suitability of this material?


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## Shecker

It was once suggested to me to run the fumes through a wet/dry vacuum cleaner containing a pool of water with a reducing agent. This was suggested for recovering Os and Ru from hot AR and running it into a solution of ammonium chloride.

Randy in Gunnison


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## Noxx

Alright, here are three pics guys:

First one, my hood and a table. 

[IMG:1024:768]http://i29.tinypic.com/2ps4tw2.jpg[/img]

Second one, close-up look at the hood. You can't clearly see it but the front panel is there. I went the cheap way and I bought an acrylic panel which is 0.08'' thick for 15 buck. I could have buy a lexan panel which is 1/4 thick for 70$ lol

[IMG:1024:768]http://i25.tinypic.com/2qtwbci.jpg[/img]

[IMG:1024:768]http://i29.tinypic.com/1q3kp0.jpg[/img]

Cutting though acrylic (of this thickness) is a real pain in the ***. It breaks very easily. I used my dremel with a pointed tip (the one with diamonds) and it works very well.

The hood and my lab are still in an early stage, I will post pics of the progress.


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## SapunovDmitry

Everything looks great Noxx.
The only thing i wouldn't do is making a plug deep inside. I have mine on the right panel near the exit. Cause when you try to turn it off (if it's very urgent) you have to be able to reach it not having your hands inside.
But though it's reeeeally nice.
Good job Noxx.


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## Noxx

Well this cabinet already had a hole in the center so I decided to put the plug there. I think I'll add a breaker at the opposite wall to shut off the entire current if needed.

Thanks for the comment.


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## Platdigger

Nox, shouldn't the vent at the top start out about the same size as the cabnet, and then taper as it goes up?

I mean just to make sure you have good even draft so you are not breathing anything.
Just seems to me. Not nocking your work. Other than that it looks great!
Randy


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## jimdoc

Here is one on Ebay for 99 cents, ending in 14 hours if anyone is near
Burke Virginia, I am 175 miles away, and with gas as high as it is and
the mileage on my truck I won't be getting it. I have seen this type at the auction I deal with, and they are nice. Don't know how it will hold up to acids, but if you get it cheap enough and your close it may be worth a try.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=150260199260&ssPageName=STRK:MEWA:IT&ih=005


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## Mida

I have just finished my fume hood and I will post a picture soon to inspire ideas to other members.
I have used a sliding glass panel,but I noticed it's too heavy,and I want to substitute it with something other.
Can someone suggest me some kind of transparent material I can use? It have to be resistant to the attack of nitric and chloridric acids.
Plexiglas isn't good because with the esposition to the fumes it became opaque......


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## Mida

Here you can see my homemade fume hood.....


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## jimdoc

My fume hood has a big counterweight that hangs in the back that
helps ease the window rise. It is kind of like the weights in older
windows. Maybe that would work for you somehow, and you could
keep your glass.
Jim


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## patgspot

Shouldn't there be an air intake to let the air flow through and pull the fumes out of the hood? It seems that that would work seeing that the fumes are heavier than air. Is this assumptiom wrong?


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## Noxx

You are right, NO2 fumes are heavier than air.
That's why the fume hood you saw on my lasts pictures is no more. I'm in the process of building a new one. 
There will be two fume exausts, one at the top and another one at the bottom.


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## patgspot

I was thinking about making a hood using an old acoustic printer cover. Remember the kind for the old noisy dot-matrix printers? They have plexiglass lid with an exhaust fan built right in. I have a few of these sitting in the shop collecting dust and they've never been used (NOS). Just for temporary until I build a real one. I'm just doing my homework before I start construction on it. Don't want to have to build it twice. These covers are very large. The kind made for the wide-carriage printers. Any opinions on this?

Pat G.


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## SilverFox

I accidently bought exactly what I needed?

At a garagesale early this spring I bought this blower fan, WHO knew I would need exactly such a device not even 4 months later.

I plan on building a equivlent fan setup simlar to what I have already seen in the pdf files.


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## Noxx

I've been looking for a blower fan like that for a while on eBay but they seem to sell for top dollar... I can't grab a cheap one. Nice find


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## LeftyTheBandit

Would the NOx corrode the metal?


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## qst42know

Without a doubt, but will work for a while.


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## Anonymous

Noxx a good source for those squirrel cage fans is combination central heating boilers. You should be able to pick one up fairly cheaply from a scrap merchant or a local plumber from a redundant boiler.


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## Noxx

Thanks for the input but I just bought one from eBay a few minutes ago.

http://cgi.ebay.ca/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWNX:IT&item=360104280092

I know it's 220V but I have it in my lab...


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## Harold_V

Squirrel cage blowers are not a great choice for this application. They tend to build up on the vanes, eventually getting fully coated. It can actually plug off completely, or throw some of the material from one or more of the vanes, leaving the blower out of balance. 

You may not experience that problem if all you're handling is slight fumes. My experience was in a hood that was used for incineration as well as chemical processing. 

There are paddle wheel type blowers that resist this problem. W.W. Grainger is a source----and there may be others. I recommend them highly. I used the design for more than ten years with no problems. I can't say the same thing for the squirrel cage, which presented ongoing problems all the time it was incorporated in my first and second generation fume hoods. 

Harold


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## Noxx

It's my second fume hood as well... But I won't incinerate in my hood so I might not experience the same problem.


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## Harold_V

It would be a service to readers to comment on that after you've used the blower for a few months, Noxx. That way they'd know to use, or not use one in future builds. It's entirely possible you'll achieve acceptable results----incineration liberates a fair amount of greasy smoke (incinerating polishing wastes from jewelers). 

Harold


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## Pawnbroker Bob

I built my Plexiglass hood using a venturi effect. Been using the same squirrel fan for 15 years. I always thought this was the way it was done to eliminate the fumes from destroying the fan. 

PB


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## Harold_V

Good design!

My hood moved roughly 1,000 CFM, with the air going directly through the blower. If you can duplicate that volume with a venturi effect, all the better. 

Considering my air went through a filter before entering the fan, I don't know that you would achieve the same success, but I sure like the idea. As the filter got loaded, restriction became a problem. 

Harold


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## SilverFox

The fan cost 2$ at my neighbors garage sale, if replacement is in order. The recovery of my losses I think will be offset by the gains of such a find.


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## elfixx

I, i'm new here this is my first post but i've been reading almost every topic for a month. I'm trying to build my own fume hood using a squirel cage blower and y pipe. Can anybody tell me why the air is blowing at both end of the pipe instead of blowing 1 way and sucking air trought the other? or can anyone post a good fume hood plan?


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## butcher

would need venturi effect, like a dredge works, or steam jet pump, water jet pump Etcetera. I have not made one sorry not much help, but this should get you pointed toward sucking air.


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## butcher

http://www.escoglobal.com/ductless/PDF/Ductless_booklet.pdf


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## Mida

The apparatus you see in the in the image is supposed to be a substitute for a fume hood,using it for small batches.Pratically,it will neutralize any toxic and corrosive vapours of AR,during the distillation.
The thing not clear to me is why you have to pass the vapour in the acetic acid solution,before to pass it trought the soda.Any suggestion?


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