Chemorg42
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What requires a fume hood?
If I am working indoors, when do I need a fume hood?
For example, is it required when making a solution of hardware store HCl? Or when using methanol or acetone as solvents?
Obviously, it is necessary if you are producing Cl2, H2S or some such, but how often is it required?
Help is greatly appreciated.
Anyone who is not shocked by quantum theory has not understood a single word. (attributed to Niels Bohr)
I think I can safely say that nobody understands quantum mechanics. (Richard Feynman)
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outer_limits
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Generally it should be used when you're working with volatile and toxic/corrosive/smelly/dangerous stuff.
You mentioned methanol - I would definitely used the hood when I would like to evaporate it.
Personally I do almost everything in the hood
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j_sum1
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And I don't (yet) have a hood. Nor do I have a gas mask with suitable filters.
I have worked with Br2, Cl2, NO2, HCl, NH3, CO and SO2 as well as an assortment of solvents (notably dichloromethane).
So, it is possible. And, I think possible to do it safely. Here are some principles:
Work at small volume. No more than is needed to get the job done. A hazard at bucket scale is a minor inconvenience at test tube scale.
Control the rate of production. I would not do anything without a pressure equalising addition funnel. Knowing you can turn it off is a huge
benefit.
Keep a clear escape route. I have had to evacuate once - in the early days of my lab, when I accidentally made a cloud of Cl2. Holding my
breath and taking two steps to the door to breathe some nice fresh air outdoors rendered the event memorable without being disastrous.
Work outdoors if necessary.
Prepare suitable scrubbers and work in a closed system. If your gas production rate is controllable then you will not overwhelm a good
scrubbing system. I have worked with chlorine without even smelling it.
Vent to outdoors if the situation demands. I have done this with a small (test tube scale) experiment that evolved CO. Less than 0.05L of gas
was actually produced but there was no harm in being cautious.
Make up appropriate neutralising solutions. I never handle Br2 without a spray bottle of thiosulfate handy. Think ahead. Do some research.
Think ahead about how you will deal with gases inside your apperatus at the end of your procedure. Again, do some research. Again, an addition
funnel is your friend. So is time: don't be in a rush.
Work at low temperature where possible. Solvents, Br2, ammonia are far less problematic if chilled.
Be married to someone who wil give you a hard time if she ever smells anything coming from the lab. (Apparently, spray lacquer for her craft
projects and hair dye don't count. But opening a bottle of toluene does.)
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Lion850
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I work in a garden shed with one door always open; and often both doors. It also has a (small) extraction fan. Follow j_sum1's advice above and you
will be ok. Apply lots of common sense, if anything starts to smell strongly switch off and vacate for a while. Be aware that warm fumes rise, often
when I get up from my chair the smell is much stronger than when I was sitting down.
Watch out for ammonia, if strong it can really hit you. Recently when I made nickel compounds I got a very uncomfortable feeling in my throat; not
really a smell but more of a strange reaction. So I will avoid working with nickel compounds. My ammonium fluoride also seems to sublimate out the
bottle as soon as it is opened, and even when closed, so it is now stored in a bottle in a bottle. I try to minimise working with it.
The smell of nitric oxide fumes always brings back pleasant memories of my lab when I was still a schoolboy 40+ years ago 
On the plus side, I have not had a cold for years
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Chemorg42
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Thanks for the advice, everyone.
To be clear, I do not have a hood myself, I am mainly trying to decide when to work outside, as well as whether to try to construct a hood myself. I
am not very handy so this is quite a dicy proposition. Still, if it is significantly better than outdoor work, I may consider it.
Anyone who is not shocked by quantum theory has not understood a single word. (attributed to Niels Bohr)
I think I can safely say that nobody understands quantum mechanics. (Richard Feynman)
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B(a)P
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I also work without a hood. Anything that would otherwise need a hood I do outside. I am lucky to have outdoor space that allows me to work with
toxic/unpleasant fumes without impacting my neighbours. One thing to consider with a hood is where would you put it and more importantly, where would
you vent it. No point having one if you can't safely direct the exhaust where it won't impact you or your neighbours.
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j_sum1
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Watching the youtube videos of UC235 is insightful. He works in his garage without a hood. He displays good practice and regularly comments on
gas-related hazards. there are some occasions where he uses a mask and he comments on why.
These clips are old but good.
(Which reminds me... I must re-watch the decomposition of polystyrene to styrene. It is one I might need to do soon.)
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Cou
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I want to work with bromoethane and other alkyl bromides. they are useful for organic synthesis, but i am concerned about their carcinogenity.
The best I can do is work outside with a heavy duty fan, wear a dual respirator, and gloves.
As much as I want to live to see the entire 21st century, chemistry as a hobby is really important to me and saved me from suicidal thoughts. and I
can't avoid carcinogens in organic chemistry.
By the time I would start facing the consequences of carcinogen exposure, e.g. 2050, biochemists may have found treatments for every cancer anyway.
[Edited on 3-6-2020 by Cou]
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Refinery
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I'm in need of a fume hood and I designed a concept already.
I make the table out of plywood with X-legs for rigidity, make a 50mm edge around the table and glue a white PE membrane on it so in event of a spill
- or for ease of cleaning - I can just wash down everything. On the other end I will place a sink.
The hood itself is made out of plywood and covered with white PE membrane as well. On the roof will be placed 3x3000lm led 5000k bulbs. Electric
outlets can be also installed.
The ventilation is done by placing an activated carbon filter inside the hood on the top corner, and an inline duct fan that sucks air through the
filter, and exhausts the fumes out from a window where an outlet is made. ACF eliminates most, but not all fumes so a check should be made upon
reactions which fumes should be scrubbed manually to minimize exhausts.
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mackolol
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I use fumehood only if it stinks in my lab. If I work with corrosive and toxic things I go outside, just as B(a)P.
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Refinery
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Certain reactions must be performed outside, you are right about that. The mere heat of carbothermic reduction is enough to lit a fume hood, not
speaking of the smoke and other fumes.
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B(a)P
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Quote: Originally posted by Refinery  | I'm in need of a fume hood and I designed a concept already.
On the roof will be placed 3x3000lm led 5000k bulbs. Electric outlets can be also installed.
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What are your plans for protecting the electronics (lights and power socket) corrosive vapours?
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Ubya
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https://leroymerlin-res.cloudinary.com/v1/DAMEO/48437
i use this to protect my outlets while not in use
[Edit by mod]
Image tags removed.
Please feel free to resize the oversized image or use the add file feature to upload it so that it displays correctly.
(I would do it myself but such things are awkward on my phone.)
[/Edit]
[Edited on 3-6-2020 by j_sum1]
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feel free to correct my grammar, or any mistakes i make
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zed
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Love the fume hood. Always used one, whenever I could. Possibly why I have grown old, and not developed cancer, the heebie-jeebies, or Parkinsons
disease. Yet.
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macckone
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Risks are relative.
Everything has a recommended exposure limit.
MSDS is your friend, use them.
Look up acute and long term limits.
Long term limits assume 8 hours a day exposure.
Acute assumes a short duration once.
OSHA has a list of limits which are based on long term exposure.
If a reaction is going to exceed the acute limit then you definitely need a fume hood.
If there is a big difference between the long term and acute limits, then you can probably exceed the long term limits occasionally.
One thing to keep in mind is carcinogen risk is cumulative not just acute.
This is also true of things that cause lung, liver or kidney damage.
Just because you breath it doesn't mean the risk is just your lungs.
Prolonged exposure to DCM vapor can cause liver damage (it usually doesn't because it takes a lot).
It is also a presumed carcinogen but it isn't in the same class as dioxin (not to be confused with dioxane).
Personally anything that produces a lot of fumes or vapor is outside or in a fume hood.
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JJay
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It's almost always possible to get by without one if you're careful with where you vent your gases, but it's good to have a stopgap measure in place
for accidents.
The only lab operation I've done where I actually needed one was distilling sulfuric acid. It was too scary-looking to do outside (I did that once...
not a good idea), and there was really no other good way to vent stray boiling hot sulfuric acid vapors that would erupt with some pressure out of the
flask at random intervals.
It almost never hurts to use a fume hood, and when I have one, I use it for anything more dangerous than pouring vinegar into a beaker. Actually, I'd
probably do that in a fume hood too.
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Frankenshtein
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What requires a fume hood?
Everything, is what I'd say because it can help contain mistakes, and because of what asking this question implies. I fell ill doing a distillation
outdoors is why I say, so maybe my perception is skewed. It was likely a result of poor planning and handling but a fume hood wouldve contained it.
You should look at MSDS for every chemical youll work with and sometimes they can provide you with information on safe handling. MSDS language looks
very shocking until you read a lot of them and realize they all have a common tone.
I look for any info I can find on a chem because sometimes you find more about one from other sources. Personally, I spend most of my chemistry time
gathering information on safety of everything I'll work with and learn much less about actual chemistry.
You can spend under $15 on an air matress inflator fan and buy some cheap ducting, if you dont have a budget enough to put together a DIY fume hood. A
little ventilatiom is better than none.
[Edited on 11-9-2020 by Frankenshtein]
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1KEE
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I'll second the "everything".
I have a small industrial shop with a fair amount of metal-working machinery, and even boiling water for long periods of time increases the humidity
enough to make stuff rust. Did one experiment with acid and next morning the rust was very obvious on machines throughout the shop. Not to mention
it's not healthy to be breathing it.
I'm really looking forward to setting up the fume hood I recently acquired, just worried that the hole in the roof I'm planning on using for exhaust
(4" bathroom fan vent) is a bit small
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zed
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Even a good fume hood isn't infallible. At some point, a combination of uncooperative prevailing winds, hood window height, and open windows or
doors, will cause your hood to not vent properly. Try to trap toxic vapors, way before your hood fan whips them up the chimney.
If you are working with something exceedingly nasty. Know when to leave the room.
And, if it is appropriate, try to utilize a positive pressure mask, supplied by remote air. A PAPR unit.
This may sound difficult and expensive, but it isn't. Just clumsy.
Hook up a 12 volt auto battery to a 12 volt 3 to 4 inch, Marine blower, outside your shop.... twenty to thirty feet from your work area . Hook the
blower up, to ductwork, or ABS piping, to blow outside air to your work space. Install a 40 mm NATO connector on your Air Supply duct, Use a regular
gas mask hose to hook up your full face gas mask to the forced air coming through the duct. You may pre-filter air, at the blower, if you wish.
Even if you lose regular power, or your hood screws up, the positive air pressure inside your mask, should prevent poisonous gases and vapors from
reaching your lungs.
You have an auto battery. You should have a full face gas mask. The 12 Volt marine blower should cost 20 to 30 bucks. Add ABS or other duct work,
and some gas mask hose. And, you are pretty well covered. Not unusual to see similar set-ups in auto paint shops. Where the painting must be done
indoors, and there is no good way to vent all of the toxic vapors.
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TriiodideFrog
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Basically stuff that gives off toxic fumes or tiny particles that may cause breathing problems.
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