Sciencemadness Discussion Board

Fume Hood Design

Xenos - 24-9-2002 at 15:25

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]

Vacuum cleaner fume hood

Rhadon - 24-9-2002 at 16:17

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.

bangandow - 17-10-2002 at 20:53

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. :(

Anarchist - 26-12-2002 at 17:31

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.

final solution: bilge fan

Organikum - 30-12-2002 at 10:31

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....)


Xenos - 13-1-2003 at 18:57

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 :D. Point being: it acually works and it prevents my garage from smelling like nitric acid or chlorine for weeks.

a few days of use

Organikum - 15-1-2003 at 16:34

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

Fumehood substitute

Hermes_Trismegistus - 15-1-2004 at 18:43

reprinted w/out permission from LabDad

Cu-hood.jpg - 27kB

Chris Owen - 15-1-2004 at 19:31

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

building hood

Jupiter - 5-6-2005 at 08:12

I am planning to built an hood using a toilette aspirator, but I am worried :o 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?

garage chemist - 5-6-2005 at 10:45

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?

12AX7 - 5-6-2005 at 15:37

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

Magpie - 1-8-2005 at 20:55

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.

Fleaker - 2-8-2005 at 13:29

A good filter material would be a column of activated charcoal especially for absorption of volatile organic fumes.

Magpie - 2-8-2005 at 17:53

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. :D

[Edited on 3-8-2005 by Magpie]

Magpie - 3-9-2005 at 13:12

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. :D

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.

Bilge Blowers!

Eclectic - 3-9-2005 at 16:02

I just discovered these. $18-32, 12v.
For venting gasoline fumes from engine compartments. :D

http://www.boatus.com/boattech/bilgblo.htm

Magpie - 3-9-2005 at 18:54

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. ;)

Eclectic - 4-9-2005 at 05:29

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]

Magpie - 4-9-2005 at 07:27

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]

Eclectic - 4-9-2005 at 16:00

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.

Magpie - 4-9-2005 at 20:59

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. ;)

static electricity question

Magpie - 5-9-2005 at 16:26

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?

neutrino - 5-9-2005 at 17:24

I may be missing something here—why is a grounding piece made of fiberglass (an insulator)?

Magpie - 5-9-2005 at 18:07

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.

Magpie - 10-9-2005 at 12:07

Garage Chemist:

I enjoyed your pictures of PCl3 production - congratulations on your success!

Your fume hood interests me as I am in the middle of making one myself. If yours is home made could you tell us a bit about it, i.e., 1) internal dimensions, 2) materials of construction, 3) do you have a sliding window (I didn't see one), 4) air flowrate 5) type (constant air flow, variable air flow, etc), 6) what you like and don't like about it, and 7) any recommendations to other builders.

I currently have my design for a hood enclosure out to a metal fabricator for bid. It will be made from 14 gauge (0.064";)(1.6 mm) aluminum.

Eclectic - 11-9-2005 at 09:36

Have you ever actually done chemistry experiments near aluminum? :o

That's sort of like making a high temp combustion boat out of magnesium. :(

Stainless steel maybe, but much better would be cement board made for ceramic tile backer, or epoxy fiberglass if weight is an issue.

Magpie - 11-9-2005 at 10:29

No I have not. But aluminum is used for all kinds of cookware, e.g., frying pans, dutch ovens, etc. I think the top of some stirrer/hotplates is also aluminum. Granted these are heavier than 14 gauge sheet. What has been your experience?

I would like to use stainless steel but am trying to keep the cost down. I am planning on placing a ss catch pan in the bottom of the hood.

Cement backer board or even wallboard (gypsum) are attractive possiblities. ;)

frogfot - 11-9-2005 at 10:46

Quote:

Have you ever actually done chemistry experiments near aluminum?


What kind of chemistry did you have in mind? :o
IMO this would be a great choise for a home lab hood, mainly due to low weight. One can always paint it if you're worried about corrosion.

I have used a hood thats made of wooden/Al pipes skeleton covered with polyethylene sheet, for a good while.. There was no noticeable corrosion on aluminium. Although it all depends on how big is the load.. I tried to keep it low due to neighbours.
Quote:

I would like to use stainless steel but am trying to keep the cost down.


But Al is alot more expensive than steel. I'd guess that 0,5mm steel would be enough if it's mounted on somekind of support (skeleton.. or how is it called).

Eclectic - 11-9-2005 at 12:49

Acids, alkalies, fertilizers, other salts, all cause corrosion on aluminum. Chlorides cause pitting and stress cracking in stainless steel. Portable benchtop fumehoods are typically made of fiberglass. For best fire and chemical resistance I'd go with 1/4" cement backer board, maybe coated with automotive or industrial epoxy. Asbestos board used to be the material of choice, except for hoods used for perchloric acid, which use stainless steel to avoid buildup of explosive perchlorate salts.

garage chemist - 12-9-2005 at 01:49

My fume hood is made of pressed wood plates (don't know the english word for "preßspanplatten";).

The fan is simply the "dunstabzugshaube" from our old kitchen. It originally carried the steam produced when cooking outside of the house through a vent pipe (so its intended purpose was similar to that of an actual fume hood). However, there was originally some kind of filter mat in it. I removed it, and now it moves much more air than before because of less air resistance.
A hole had to be made in the wall of my garage in order for the vent pipe (PP sewer piping) to be put through.

The speed of the fans (it's actually two in one casing) is controllable in four steps. I don't know the flowrate, but it's not exceptionally high.

There is no sliding window on it, the PMMA window is stationary.

More pics of my hood: http://versuchschemie.donau-it.de/topic,4457,-Mein+Abzug.htm...

My recommendations for other builders:
DO WHATEVER FLOATS YOUR BOAT.

You need to define the dimensions of the fume hood according to the type of apparatus you want to build and operate in there.

You can use whatever fan is available given that it moves enough air for you to feel safe from toxic fumes.

And don't try to attach any type of scrubber or filter to the air outlet. It will either not work or it will severely obstruct the air flow, I promise you.
Instead, use a stronger fan to dilute the fumes.

And last but not least: don't put too much money into it. Better save some money for glassware. You will never be able to do real chemistry without a ground- glass distillation setup. I always pity the people who say that they are doing "chemistry" and try to make, for example, nitric acid without distillation or in an improvised still. Even a small still (mine has only 160mm condenser length and NS 14/23 on all joints) is of extraordinary usefulness.

[Edited on 12-9-2005 by garage chemist]

Magpie - 12-9-2005 at 10:00

Thank you garage chemist. FYI I think the word you were looking for is "plywood."
I looked at the pictures - the lawn chairs and shrubbery off to the side is a nice touch. :D

Frogfot: I did some pricing for sheet metal this morning. The results for a 4'x10'x0.063" sheet:

stainless steel: $228
aluminum: $93

So for me aluminum is cheaper.

frogfot - 12-9-2005 at 21:55

That's a strange metal supplier. Mine takes money for kg of metal (plus some money depending on size of order), and Al is defineatly more expensive by weight. I'm currently bying metals from local recycling center, they take only for kg prise.
Quote:

Acids, alkalies, fertilizers, other salts, all cause corrosion on aluminum.


The fumehood walls is normally in contact with minute amounts of corrosive things. Unless your reaction vessels explode often.
Anyway, it's best to paint any metal..
Quote:

And don't try to attach any type of scrubber or filter to the air outlet. It will either not work or it will severely obstruct the air flow, I promise you.


Easy for you to say.. :P
I live in an appartment house, and the neighbours can pretty much sence when I fart in my appartment.. :(

[Edited on 13-9-2005 by frogfot]

DetMar Bilge Blower

Eclectic - 14-9-2005 at 09:12

Ok, I've gotten two of these to experiment with. They are basically a permanet magnet 12 VDC motor with fan mounded inside a 4" (100 mm) molded pipe section.
The motor can be voltage throttled, and I suspect can be driven from 115 VAC with a simple circuit consisting of a capacitor, resistor, and diode. This could be controlled with a standard lamp dimmer. If the tabs for attaching flex hose are cut off, there is a good fit with 4" PVC SWD drain pipe (only $5 or so for 10 feet). More later, maybe with photos if any one is interested.

[Edited on 14-9-2005 by Eclectic]

TheBear - 20-2-2006 at 13:13

I'm constructing a new fume hood and I would really appreciate any suggestions for improvements. It's made out of galvanized steel plates and aluminium bars:




I'm thinking of mounting cement backer boards on the inside of the walls and on the bottom and "ceiling" of the hood as well. The cement backer board is "minerit" board and is supposed to be water resistant. But any acid spills would probably ruin it in no time at all. So I think I would like to paint them. Expoxy paint was suggested by Eclectic. Is it compatible with minerite, does it provide good adhesion (pH 11 on the surface is stated for minerit, and "alkali resistant paint" is recommended). What about silicate based paints? Would that improve acid resistance of the cement based board?

Im also thinking of of just painting the galvanized steel plates, or perhaps doing both? What do you suggest?

Here is some data for minerit: http://www.americanfibercement.com/minerit.html

By the way, just ordered some plexiglass to be cut up for a sliding windows and a fixed window. When finnished, I could upload a picture of the fume hood if there is any interest.

[Edited on 20-2-2006 by TheBear]

[Edited on 20-2-2006 by TheBear]

Magpie - 20-2-2006 at 14:12

I have had my fume hood in frequent use now for 4-5 months so feel that I can comment on its performance.

1) Air flow is strong, but not too strong and seems to be well distributed.

2) Because I have good airflow I feel that the choice of wall and ceiling material is not so important. Contaminants are quickly diluted and carried out of the enclosure. I see no evidence of corrosion on the walls or ceiling.

3) Yesterday I inadvertantly forgot to turn on the blower while dissolving tacks in HCl at boiling. My 1000 mL beaker was covered with a watch glass. I went to watch TV for an hour or so. When I went out to the garage the air was so bad that I could barely get to the hood to turn on the blower and cut the heat. After about an hour with the blower on it was as if nothing had happened. No evidence of corrosion on the epoxy painted walls/ceiling.

4) I really like the stainless steel pan I use for the floor of the hood. This has rounded edges and the walls are 25mm high. I'm always spilling a little reagent on this but it cleans up easily and shows almost no corrosion.

Comments on your design:

1) I would tend to not install the backerboard but paint the galvanized steel with epoxy instead. Simpler and easier to clean.

2) Is this big enough? Mine is 1.33m wide which is plenty big if I didn't store all my liquid reagents in it along the sides. With this storage it is just big enough for any complex glassware setup. And my glass is only 19/22 taper size.

3) Give some thought to your airflow pattern. Will you be installing any baffles to direct flow. What will be your face velocity. Will it be a constant volume type or is airflow restricted when you change position of the window?

4) How does air get into your room when the blower is running? I installed a screened, louvred vent (~ 30cm x 60cm ) that vents into my house attic at the peak. Outside air then comes in through the soffet vents, travels through the house attic, and then through the louvred vent into the garage. If I stand below that louvre I can feel the airflow when the blower is running. But I am moving 400-500CFM. If you are using a much smaller blower this may not be necessary.

No matter what you do you will be much better off than not having any hood. ;) If you have any questions please fire away!

Flip - 2-3-2006 at 21:05

Once in a chem lab I saw a "fume hood" that was really just a 4x3x2 plastic box with some large hose attachments, open to the front with a plastic screen that slid up and down. Looked lightweight and portable. I'll see if I can't make a phone call tommorow and get a brand name on it, but it didn't look too expensive, and you could have a ventilation system set up with different types of fans that might blow the vapors into a bucket of a solution or even out a window : )

Has anyone seen what i'm talking about?

TheBear - 3-3-2006 at 13:18

Thanks for your comments Magpie. I've reconsidered since reading your post. I won't or will at least wait with installing additional boards covering the walls. For now I might actually use it "as is" and see how things develops, if any leakage is seen (all sides aren't completly sealed) or if the steel starts corroding.

Flip - 9-3-2006 at 18:32

Here is something I sketched up a couple of days ago. I'm going to build it out of wood, and use an epoxy paint or PVC sheeting on the inside.

fumehooddesign.jpg - 50kB

TechnologicallyRetarded - 14-9-2009 at 14:07

These plans are looking great! I too really need to get one of these up and running.

In my rudimentary drawings, I stop when I reach 'duct'.

Do you have any plans for scrubbing fumes - not for the 'eco-points', but for keeping neighbors alive - or do you plan to let them flow into the surroundings?

I'm not going to lie: my main concern is safe removal of NOx. Are there any extra bits I would need to add for that?

MeSynth - 14-8-2011 at 21:22

Quote: Originally posted by Flip  
Here is something I sketched up a couple of days ago. I'm going to build it out of wood, and use an epoxy paint or PVC sheeting on the inside.


That picture kicks ass....

MeSynth - 14-8-2011 at 21:39

for a really fast temporary fume hood all you need is a card board box, a bathroom vent fan from home depot, some aluminum ducting, some aluminum tape, some painters plastic (used to catch paint), and some glue.

after your done all you have to do is remove the ducting from the fan and cut out the vent fan then jump on it repeatedly and toss it in the trash.

the painters plastic is used to line the inside and to act as a semi see through air barrier to allow for efficient air flow.


THE BEST think you can do when it comes to fumes is use a distillation apparatus. Instead of boiling off solvents you distill them off in a closed all glass setup with glass joints with a tube connected to vacuum nipple directed toward some kind of vent or hanging out of a window if your desperate. As opposed to the guy who boils off a liter of volatile hydrocarbons and stinks up his entire block with it. You know who you are... *serious face*

To go the extra mile you can pass the fumes or gases through scrubbing solution and/or passing the fumes or gasses through an activated carbon filter. The scrubbing solution and carbon can then be taken care of by your cities hazardous waste program or dumped into the middle of your cities busiest intersection. The latter is not advisable...

My Designs

Un-Sub - 30-10-2011 at 12:01

These are the designs I will be Fabricating soon! Let me know what you people think!

Will it work?

This is the air scrubber I will be using.

Air Scrubber


this is the design for my Fume hood.
Attachment: IMG_0001.pdf (798kB)
This file has been downloaded 765 times

[Edited on 30-10-2011 by Un-Sub]

This is the design on my exterior diffuser.
Attachment: IMG_0002.pdf (591kB)
This file has been downloaded 705 times

[Edited on 30-10-2011 by Un-Sub]

[Edited on 30-10-2011 by Un-Sub]

[Edited on 30-10-2011 by Un-Sub]

Un-Sub - 31-10-2011 at 13:17

OK. I got my photos converted and uploaded. I need someone who knows something about fume hoods and diffusers to take a look and give me some feed back!

The hood will be small, ( 24"H x 24"D x 36"W ) I believe that is 12³f, and the blower pushes 160³f/m. The shell will be 1/8" steel plate and the doors and view top will be plexiglass.



Do you think this diffuser will work, or will it be a problem with the fumes combining with the water and creating acids and such?
Now remember, this will be after the fumes have passed through an 8" diameter activated carbon fiber filter!



So, what do you guys think?
Will it work?

watson.fawkes - 31-10-2011 at 17:13

Quote: Originally posted by Un-Sub  
Will it work?
Will it work for what? You really need to say what you're trying to do. If you're trying to set up a distillation rig with two feet of vertical clearance, you'll have, er, trouble.

Fume hoods are ventilation devices. With 160 cfm, you're hardly moving much air. What's the face velocity with the doors open? What's your dilution ratio for an expected gas generation "event" within the hood?

Remember that particles can be generated within the hood. Most hoods exhaust particles from the hood along with the rest of the gas stream. Filtration, if needed, happens later. What you've got set up looks certain to clog in many plausible circumstances.

As for the scrubber, it's all about contact time and surface area. That means you want tall and narrow over short and wide. It's easier to scrub arbitrary atmospheres with mists rather than bubblers.

Magpie - 31-10-2011 at 17:31

Quote: Originally posted by garage chemist  

And don't try to attach any type of scrubber or filter to the air outlet. It will either not work or it will severely obstruct the air flow, I promise you.
Instead, use a stronger fan to dilute the fumes.


I think that is good advice.

Un-Sub - 31-10-2011 at 19:12


@Watson.Fawkes

I am not sure what it will be used for, I am new to chemistry and can't say what exact experiments will be done in it. Since I know jack about chemistry I will be starting on Youtube replicating some of NurdRage's experiments. It will not be used for distillation.

As for the face velocity, I don't know, it hasn't been built or the parts bought yet. I am trying to figure out what will work w/o spending a fortune. Like...a couple hundred bucks!

I can't just dilute the fumes with high air flow, I also have to get rid of the smell, I live in an apartment complex.

As for the dilution ratio for an expected gas generation "event" within the hood......ummm....what?

As for the clogging problem, what would you suggest using and at what point in the exhaust system?

As for the mist instead of a bubbler, what about both? Would it work to add a water pump into the box with a hose running up top to a mist head?


@Magpie

I have to have some kind of filtration, my lab is going to be built on my Apartment patio, I don't want to render my neighbors unconscious or worse and I have to get rid of the smell!

Tell me where I'm going wrong and what to do to fix it!

[Edited on 1-11-2011 by Un-Sub]

Magpie - 31-10-2011 at 20:16

It is possible to use a scrubber, industry uses them commonly. But they must be carefully designed, or expect a lot of trial and error until you get the system balanced. A packed scrubber will flood, just like a distillation column, if the gas velocity is too high.

You would have to mostly know accurately what your air flow rate will be. 160cfm is a nominal value at some assumed pressure drop. This not rocket science but some engineering is involved. Otherwise you could be in for some lengthy and expensive trial & error until you get the scrubber sized correctly. That is why my first advice was to avoid it.

Also, do you plan to operate with the doors closed and just use the glove ports, or will you have the doors open? Your answer will affect the flow rate significantly.

In the winter your exhaust is going to be a horribly visible stream of fog, like a clothes dryer exhaust. Are you OK with that?

Un-Sub - 31-10-2011 at 21:04

@ Magpie

Would the scrubber be better if it were installed vertically instead of horizontally? What do you think the minimum airflow should be for 12 cubic feet of space? I can purchase a different scrubber that is longer and more narrow if it would be better.

what about something like this:
ebay air scrubber

I plan to use it with gloves and with the door open, depending on the experiment, but I can put in more intake vents and make them larger if needed. How many do you think I would need and how large?

As I stated earlier, I have not even started on this project yet. I want to make sure everything is right before I start the fabrication process!

As for the exhaust being seen, that doesn't matter at all, as long as the air is clean and doesn't smell bad!

Magpie - 31-10-2011 at 21:38

Quote: Originally posted by Un-Sub  
I want to make sure everything is right before I start the fabrication process!


That is wise.

Here's some documents you should review:

http://www.s-k.com/pages/pro_07_02.html

look at the bulletin 7S toggle.

Don't bother with the ejector, but look at the packed column and the "venturi scrubber" designs - just for ideas.

http://ehs.columbia.edu/FinalLabDesign4-09.pdf

Note the statement at 7.4

Un-Sub - 1-11-2011 at 05:08


What type of mist are we talking about here?
are we talking fine mist or a conical of high pressure water?

I have another problem here, I don't have a gas treatment plant at my disposal, so I can't drain my water, it will have to be recycled into the box.

I see what your getting at though, what would withstand the chemicals better: Stainless Steel, Steel or brass? ( for the water jet)

I am going to revamp my schematics, I will post what I come up with.

I have come up with a couple ideas for the wet scrubber, but I have to recycle my water. Would a sand and carbon fiber bed work to filter the water, if it is elevated so the water can strain through? Then be pumped back up to the water jet.

[Edited on 1-11-2011 by Un-Sub]

[Edited on 1-11-2011 by Un-Sub]

watson.fawkes - 1-11-2011 at 07:49

Quote: Originally posted by Un-Sub  
I am not sure what it will be used for, I am new to chemistry and can't say what exact experiments will be done in it. Since I know jack about chemistry I will be starting on Youtube replicating some of NurdRage's experiments. [...]
I am trying to figure out what will work w/o spending a fortune. Like...a couple hundred bucks! [...]
I live in an apartment complex.
I don't mean to discourage you, but I have a different suggestion. If you're this new to doing chemistry, wait on getting a fume hood and, in the interim, do experiments that don't require one. There's lots of chemistry to be learned with reactions that don't do anything particularly noxious. Our member woelen here has a web site plenty of such. http://woelen.homescience.net/science/chem/index.html

The envelope of your understanding, location, and resources seems to me like trying to more than one impossible thing before breakfast. Of old, the original chemists had reputations for living in marginal areas and making horrible smells. There's a lot of truth to that combination. There's a minimum combination of remoteness and equipment that's needed to deal with smells. If you're not remote, like an apartment complex, then you need more budget to acquire the gear needed to deal with in. And since you don't have a lot of space, that gear needs to be compact, which makes it more expensive, whether you build or buy it.

You're in a position here that many new members are, full of enthusiasm to learn, but without a lot of knowledge or budget. The issue is that without knowing either exactly what you're after or how to accomplish it, you're not likely to come up with something that's satisfactory. One idea that's more likely to get you good results in this initial period is to get the equivalent of an old steamer trunk and make a portable lab kit for the experiments you want to do. Then travel to a remote location for chemistry. Many experiments that require a fume hood can be done outdoors instead. This is a way of buying remoteness. If you do this for a while, you'll get a better idea of what you want.

Therefore, I'd like to ask you some questions that will help you learn more about what you want to do and how to deal with the consequences. List five experiments you want to do that you think require a fume hood. With each, tell us what you want to learn from it and why you think you need a fume hood for it. You're sure to get good advice here if you say what you ultimately want.

One last observation. If you're in an apartment, I'd be concerned first with making sure you've got a good way of dealing with drainage and spills. That may be more limiting to you than not having a fume hood.

Magpie - 1-11-2011 at 11:49

I have taken two full years of university level organic chemistry. The first year was in the 60's for my BS degree in chemical engineering; the 2nd was as a refresher course after my retirement in 2003. In neither course did I have a fume hood. As watson says there is a lot of good chemistry that can be done without one.

Do the experiments on a small scale - a few grams at most.

Many noxious and stinky gases can be absorbed with a small bubbler and the appropriate absorbent solution, right after the point of generation. For example, H2S can be absorbed in an aqueous solution of NaOH. HCl can be absorbed in water using an inverted funnel placed very near the water surface in a beaker. If peach was commenting here he could give you more examples as he is a big advocate of such methods.

Use the wind to your advantage. As evil lurker once said, when the wind direction and speed are appropriate, he is "good to go."

Get a year or two of experience under your belt then re-evaluate your need for a fume scrubber and carbon absorber.

Roachburn - 2-11-2011 at 04:47

I saw a video on synthesizing nitric acid and the guy sends the excess gas into a solution of sodium carbonate and water neutralizing the NO2. would this work with other gasses? what about NaOH? Doesn't that absorb gases?

Un-Sub - 2-11-2011 at 06:57


Well, you guys have convinced me. I don't know anything about chemistry and I obviously can't afford it, so I'm gonna find something else to do as a weekend hobby!


Thanks for the feed back from all you guys. Have fun with your experiments!