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Author: Subject: homebuilt fume hood
watson.fawkes
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 Quote: Originally posted by watson.fawkes Opening this damper will lower the face velocity, just as opening the damper on the outlet of the hood will.
Oh, the typos. This sentence should read as follows, with one important word change:

"Opening this damper will lower the face velocity, just as closing the damper on the outlet of the hood will."
Neil
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I modded a computer power supply to run tandem engine room exhaust blowers from a local boating store. Each blower is rated to 230CFM and were something like 30$each - which is significantly cheaper then a bathroom or range hood fan blower with the same CFM. (To get 460 cfm with bathroom fans I was looking at having to spend 300$ or more)

These blowers are explosion proof and can be for only a few more dollars, water proof. I got the idea from the other fume hood thread.
Kiwichemicali
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Alternative?

What do you think of an extraction arm as an alternative to a fume hood for a hobby chemist?

Kiwi

<img src="http://www.cleanairco.com/public/images/products/extractionarms/alsident/026%20100%20CR.jpg" width="300" />

<!-- bfesser_edit_tag -->[<a href="u2u.php?action=send&username=bfesser">bfesser</a>: reduced image size(s)]

[Edited on 7/12/13 by bfesser]
CaptainOfSmug
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I think that would work just fine. I use something similar except I have my fan connected to ducting with a carbon scrubber attached. I like it more than a fume hood in some respects because I can simply move the duct attached to some rails on the ceiling over where I'm currently experimenting.
hyfalcon
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Just picked up 3 of these PSC blowers. I pad less than $100.00 shipped on an offer. First piece of the puzzle for a fume hood. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=26122... [Edited on 12-7-2013 by hyfalcon] PeeWee2000 Hazard to Self Posts: 58 Registered: 2-7-2013 Location: Michigan Member Is Offline Mood: No Mood Heres my craigslist found 15$ 3/4 HP furnace blower mounted in the window next to my lab table. I just screwed it to the window and sealed i up with plastic sheeting and duct tape . I cant say its safe for playing around with toxic fumes and such but its proven to be enough to keep explosive vapors (e.g. Diethyl Ether) from building up. Does an excellent job of keeping me cool with all my safety stuff on too!

Upsilon
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Building a fume hood

As many people before me have probably figured out, it seems rather useless to spend $1000+ on something that wouldn't be very difficult to build yourself. Anyway, I'm trying to build my own fume hood, and I was wondering if anyone had any tips. I am planning on making the main structure out of wood, with aluminum sheeting to line the interior to prevent the whole thing from burning down. Over the aluminum would just be some cheap replaceable plastic sheeting to prevent corrosion of the aluminum. Also, does anyone know of a fairly cheap fan that can move a lot of air? I'm just asking for tips from people who have done this before. Dariusrussell Hazard to Self Posts: 70 Registered: 27-6-2013 Location: Southie Member Is Offline Mood: Organometallics There are many many many...many many threads on this. Do a search next time. As for your design, it seems fine, I would suggest you do a spray on enamel or epoxy in lieu of the plastic sheeting. I assume your going to use very thin aluminium, I would suggest backing it with 1/8th in MDF/Plywood/Particleboard so that you can mount things to it. As for the fan, You want a squirrel cage blower. Its preferable to have one where the motor is on a belt, but at the very least use one with the motol not built into the fan. I also suggest that you spray all parts of the system in an epoxy/enamel spray to prevent corrosion. http://bit.ly/190UNMo, I'm lazy heres the google search Gooferking Science Hazard to Self Posts: 97 Registered: 17-7-2013 Location: Somewhere in Kansas, USA... Member Is Offline Mood: Halogenated I have a four part tutorial on making a fume hood on my youtube channel. The link to my channel is in my signature. The total cost is about$150. I have used the hood many times and it seems to work perfectly.

bfesser
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13-10-2013 at 17:38
bfesser
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Admittedly not suited to all tasks, but I like the simplicity of this design. I think I'll try building one.

[Edited on 2.1.14 by bfesser]

subsecret
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This is a very interesting fume hood design that I found...It's got a Venturi-type arrangement.

My fume hood (I understand that this is crappy) is a wooden box with a bathroom exhaust fan connected to the top. It exhausts through a good length of 4 inch dryer exhaust hose, which is connected to a board shoved in the window and held via a dryer termination (with flaps). The fan moves about 50CFM (not much at all, I understand), and the face velocity is very low. I plan to connect an inline fan between the end of the dryer hose and the wall termination, creating negative pressure along the entire length of the exhaust system (no chance of fumes escaping). This would work in series with the bathroom exhaust fan, though it may be removed entirely. After testing with ammonium chloride fumes, it's very rewarding to see a thin cloud forming outside the basement window.

I may ask my brother if I can use his massive cage fan for a new design. It's termination is a 6 inch round duct, and it pulls a lot of air. The only problem with it is that the motor is placed inside the fan drum, though it is sealed entirely (I assume that cooling slots were not necessary because of the massive amount of airflow).

Fear is what you get when caution wasn't enough.
nanobot-dnp
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Dont forget that it's not just all about the amount of air your fan can pull. You also need to bring the same amount of air into the room.

[Edited on 8-1-2014 by nanobot-dnp]

evil twists what is already there
Jmap science
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Making My Fume Hood

Yesterday I started on my fume hood. I am going to put it on my desk and the duct fan goes from the hood to outside. It is 30" deep, 36" high, and at the top there is a plexiglass face shield.There is a Led light in it and also a plug and gas connections, it has a small shelf in it.

I am going to use it for things like making benzene or diethyl ether to flash powder. do you think there is any other thing I need to add to it?

[Edited on 25-1-2014 by Jmap science]
TheChemiKid
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Maybe you could add a vacuum connection if you have a pump.

When the police come

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bfesser
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25-1-2014 at 10:46
bigmol
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Like many commercial labs I dont have a fume hood instead the whole lab is treated as a fume hood with a large exhaust fan and crossflow ventillation. The whole lab air change is only a few minutes.
If there was anything to bad I would use a glove box under a slight vacuum
subsecret
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Sorry to post in such an old thread, but I just got an idea for a cheap, somewhat chemically-inert fume hood fan.

I just bought one of these online: http://www.amazon.com/Diversitech-625-AF6-Round-Duct-Fan/dp/...

To make an externally-driven fan, the motor and blade of the fan would be removed, and the blade would be mounted to a longer steel shaft using epoxy glue. Next, the empty fan housing would be sealed to a metal tee fitting, so that the fan attaches to one opening of the top of the "T." A flat stovepipe cap with a hole in it to accept the extended shaft would be attached directly opposite the fan housing, and the blade with the extended shaft would be passed through the original motor mount and the hole in the cap, so that it protrudes from the outside of the cap. A plastic bearing (possibly with an oil wick) could be made to prevent the shaft from abrading. Next, the motor would be attached to the outside of the cap with pieces of wood, and the shaft would be attached with a piece of tight-fitting PVC tubing or a setscrew connector.

This way, the motor is not exposed to fumes, and most of the system can be under negative pressure to prevent leaks.

Fear is what you get when caution wasn't enough.
Hellafunt
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since this thread is resurrected from the deep sleep, maybe i could ask a question. ive been working on my fume hood for a few weeks, and its almost finished. im excited. it is made of 1/4" plywood with a frame of wooden slats taken from an old futon. it has a used window in the front, and ive purchased a dayton blower fan for it. im about 75% finished building it, but i still have not decided on lighting.
ive read through what i think is all the fume hood posts on the site, and ive come across very little about lighting the fume hood. ive seen mention of explosion proof lighting, some talk of mounting lights on the outside shining through the sash to the inside, and ive considered using battery operated LEDs. My computer is very old and ive been unable to open a lot of the photos people have posted of their DIY hoods. the imageshack pics are some that i can NOT access. anyway, any brilliant (ha!) ideas?

[Edited on 20-12-2014 by Hellafunt]
subsecret
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You could simply buy some Chinese LEDs and solder them up in parallel, and put the string inside a clear piece of tubing. It may not be explosion proof, but it's easily replaceable.

Fear is what you get when caution wasn't enough.
Magpie
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This is what I did for lighting. Ie, two 4 ft, 40w fluorescent lamps mounted on a piece of glass silicone caulked to the hood roof:

[Edited on 20-12-2014 by Magpie]

The single most important condition for a successful synthesis is good mixing - Nicodem
Hellafunt
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thanks awesomeness, magpie. magpie, your fume hood has been an inspiration for me, however, my fume hood needs to be portable, i need to drag it out when i want to use it. i need to keep it as light as possible, it is already getting pretty heavy. i like the LED idea.
Lambda-Eyde
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Any thoughts on mounting the fan intake on the bottom of the hood? I've realized that I have no choice but to place the fan under the hood, as the ceiling height in my lab is only 2.1 meters. How would you make proper baffles? Obviously you wouldn't want a spill to end up inside your fan. Something like a double set of baffles (Edit: s/sash/set of baffles/), like below, maybe? How do you prevent standstill near the ceiling (since air moves both in and out near the bottom)? While still making sure that you're sucking dense vapors and gases out, instead of letting them flow out the sash? Splitting the intake into channels that go further up? How does one accomplish this without losing fan pressure which will already be hurt by three 90° bends after the fan?

 Code:  │ ││ │ ││ │ │ │ ││ │ │ <-- │ └─────── | V 

Also, making space for a 4" duct at the base of the hood means sacrificing a lot of valuable space. Are there any obvious disadvantages to doing a 4" round to, say, 20-30 x 5 cm square transition at the opening?

 Quote: Originally posted by Hellafunt thanks awesomeness, magpie. magpie, your fume hood has been an inspiration for me, however, my fume hood needs to be portable, i need to drag it out when i want to use it. i need to keep it as light as possible, it is already getting pretty heavy. i like the LED idea.

Just buy a complete LED strip instead of bothering with soldering. They can be bought complete with transformers (which you of course want to mount on the outside) for very cheap at DealExtreme, among other places.

[Edited on 30-12-2014 by Lambda-Eyde]

[Edited on 30-12-2014 by Lambda-Eyde]

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Magpie
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 Quote: Originally posted by Lambda-Eyde Any thoughts on mounting the fan intake on the bottom of the hood?

I think it could be done - with proper design.

 Quote: Originally posted by Lambda-Eyde How would you make proper baffles?

Your sketch is on the right track I think. By proper sizing of the baffle openings you can direct flow to give an even sweep over the hood working areas.

 Quote: Originally posted by Lambda-Eyde Obviously you wouldn't want a spill to end up inside your fan.

If you mount the outlet a few inches above the hood floor this would not be a concern.

 Quote: Originally posted by Lambda-Eyde How do you prevent standstill near the ceiling ...?

By having an opening at the top of the back wall through use of a baffle, as you have shown. This opening would be something like 2" x 48", assuming a 48" wide hood.

 Quote: Originally posted by Lambda-Eyde How does one accomplish this without losing fan pressure which will already be hurt by three 90° bends after the fan?

That's going to be the real challenge. You have to have a fan with a characteristic curve (delta P vs flow rate) that will give you adequate flow to provide the hood face velocity of ~1 ft/s.

You are severely hampered right from the start with a small duct size like 4" diameter (A=12.6 in^2). The 25cm x 5cm duct size would be significantly better (20 in^2), even with the square corners.

FYI my duct diameter is 8". This gives 4X the area of a 4" duct.

 Quote: Originally posted by Lambda-Eyde Also, making space for a 4" duct at the base of the hood means sacrificing a lot of valuable space. Are there any obvious disadvantages to doing a 4" round to, say, 20-30 x 5 cm square transition at the opening?

See above comment.

The single most important condition for a successful synthesis is good mixing - Nicodem
Hellafunt
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im very excited to report, that after 4-5 months of stopping and starting, working and procrastinating, my fume hood is essentially finished. id like to thank you guys , i gleaned so much info from this forum, i wouldnt have been able to do it otherwise. My friend Dave did the work that required skill.
ill try to get some pictures up. it is a little different than most because it is not a permanent install. I live in a 450 Square foot studio, and im a renter. but it is not a plastic flimsy box made up of tupperware. its made from .25" plywood, it has the corners and edges reinforced with aluminum, and a dayton blower. and a used window in the front. and baffles in the back.
tonight we did a tester. i had a coffee filter that had been used to filter some homemade KClO3. i sprinkled it with sugar, and then broke up some sticky KNO3 and sugar smoke bomb on top. we lit it and the box filled with smoke and i got nervous. but i flipped the switch, and damn, it worked. im excited! tomorrow, i get to make some nitric acid without holding my breath!

[Edited on 8-3-2015 by Hellafunt]
subsecret
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What about a perforated tabletop with an intake plenum underneath?

Fear is what you get when caution wasn't enough.
Zombie
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The only issue I see with that is you need to contain spills if equipment fractures or falls over.

I was thinking along the same lines at one point.

It's actually safest to have the air draw everything away from you via a front opening.

They tried to have me "put to sleep" so I came back to return the favor.
Zom.
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 Sciencemadness Discussion Board » Fundamentals » Reagents and Apparatus Acquisition » homebuilt fume hood Select A Forum Fundamentals   » Chemistry in General   » Organic Chemistry   » Reagents and Apparatus Acquisition   » Beginnings   » Responsible Practices   » Miscellaneous   » The Wiki Special topics   » Technochemistry   » Energetic Materials   » Biochemistry   » Radiochemistry   » Computational Models and Techniques   » Prepublication Non-chemistry   » Forum Matters   » Legal and Societal Issues