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Author: Subject: What requires a fume hood?
Chemorg42
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[*] posted on 2-6-2020 at 13:30
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.




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outer_limits
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[*] posted on 2-6-2020 at 15:02


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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[*] posted on 2-6-2020 at 20:00


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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[*] posted on 2-6-2020 at 20:16


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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[*] posted on 2-6-2020 at 20:35


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.




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[*] posted on 2-6-2020 at 21:23


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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[*] posted on 2-6-2020 at 21:39


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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[*] posted on 2-6-2020 at 22:49


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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[*] posted on 3-6-2020 at 00:33


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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[*] posted on 3-6-2020 at 01:01


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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[*] posted on 3-6-2020 at 01:11


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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[*] posted on 3-6-2020 at 02:49


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.



What are your plans for protecting the electronics (lights and power socket) corrosive vapours?
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[*] posted on 3-6-2020 at 03:53



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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