itb2003
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Question about fume hoods.
I have a few questions mostly about fume hoods I might need to make another topic for some of them.
-I saw some posts on DIY fume hoods here and I was curious what the holes at the very top of the sash are for and/or are they even needed? I'm
guessing this is used to direct airflow.
-I was also curious about the very end of the fume hood where the exhaust comes out...it looks like people use a stack high in the air to let out
there exhaust although it looks like some of the diy ones use horizontal outlets...I was curious is this done with carcinogenic materials also? Or
are there scrubbers or does it become so dilute in the air it doesn't matter?
-How do you make your sash air tight? Or does it matter since the air will be going in anyway?
-I found a big motor around 720cfm but its 8inches and my exaust will be 6inches with probably 3 90degree bends in it....will this make it push much
less feet per minute with those loads and by how much?...or does this one require experimentation or maybey I should just get the 6inch fan?
-Last question...I was reading some posts about people describing the smell of benzene lol isn't this carcinogenic?? Maybey a little isn't harmful or
is it cumulative like radiation? Not that I will try to smell it lol.
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vmelkon
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Don't know about your fume hood.
Benzene is a known carcinogen but like other carcinogens, it depends on exposure (amount and time length). Benzene is something that is added to
gasoline in certain countries, so most likely, we are all smellers of that sweet smell.
http://www.cancer.org/cancer/cancercauses/othercarcinogens/i...
[Edited on 26-1-2013 by vmelkon]
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itb2003
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Wow interesting it looks like benzene is used in lots more than I knew about.
Here's a picture I got off the forum to clarify more about one of the questions I had. There's the sash and then above it there seems to be openings
for air I've seen on a lot of diy drawings for hoods this way...is that needed and why?
I figured out the motor question allready, you would just add a motors seperate from your main motor with its own seperate ducts to add more cfm.
Also if you know the answers to the rest of my questions below that would be awesome : )
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itb2003
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I think I finally figured out another of my questions..the slots at the top are bypass slots so the fume hood can sustain constant face velocity
instead of increasing velocity when you close the sash...I think I would just vary motor speed though...
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blogfast25
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Quote: Originally posted by chemrox  | | The opening at the top is also good for evacuating the lab when the hood door is closed. I run all my ventilation through the hood.
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There's a thread on homemade fumehoods sowhere here. I wish someone would dig it up...
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chemrox
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The opening at the top is also good for evacuating the lab when the hood door is closed. I change air every 2 min through the hood. Before the hood
I had a glove box with a disposable filter. Small hoods with filters are fairly common. But I have chlorinated solvents in the lab and bromine,
SOCl2 and PCl3 in the hood. I generate HCl in there as well. Having a hood almost completes my lab. I would like even more space. It would be nice
to have a dedicated area for the Parr reactor. The vacuum cart gets in the way sometimes and I could use running water on both walls. But all in all
it works pretty well. It's just that I like to have 2 or 3 synths going at a time.
"When you let the dumbasses vote you end up with populism followed by autocracy and getting back is a bitch." Plato (sort of)
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Magpie
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Here's one:
http://www.sciencemadness.org/talk/viewthread.php?tid=11145
The single most important condition for a successful synthesis is good mixing - Nicodem
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itb2003
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Yes that's the thread I read on diy fume hoods but I didn't find all the answers I was looking for in there..
I just have two more questions that haven't been answered yet although I think I have the answers to them...however I would like it if someone could
confirm what I think.
-I was also curious about the very end of the fume hood where the exhaust comes out...it looks like people use a stack high in the air to let out
there exhaust although it looks like some of the diy ones use horizontal outlets...I was curious is this done with carcinogenic materials also? Or are
there scrubbers or does it become so dilute in the air it doesn't matter? I'm guessing all chemicals are just vented out the top though with no
filtration necessary...in a lab setting anyway....guessing industrial would be different?
-How do you make your sash air tight? Or does it matter since the air will be going in anyway? I'm guessing this doesn't matter at all...except
maybey lower face velocity by the tiniest fraction.
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Magpie
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| Quote: Originally posted by itb2003 |
-I was also curious about the very end of the fume hood where the exhaust comes out...it looks like people use a stack high in the air to let out
there exhaust although it looks like some of the diy ones use horizontal outlets..
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Use either method. Which one would you like your neighbors looking at?
correct
| Quote: Originally posted by itb2003 |
-How do you make your sash air tight? Or does it matter since the air will be going in anyway? I'm guessing this doesn't matter at all...except
maybey lower face velocity by the tiniest fraction.
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correct
The single most important condition for a successful synthesis is good mixing - Nicodem
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