Sciencemadness Discussion Board

fume control

Yttrium2 - 9-12-2015 at 07:01

How do you all deal with fumes when filtering solvents and such. I know a fume hood will evacuate the smell into the outsides, but what then? Won't that leave your neighborhood reading of solvents?

In chemistry class we put a beaker over our vessel containing solvent, this supposedly reduced fumes in the lab. How is this so? Wouldn't it just contain the fumes or would it prevent more fumes from be generated?

careysub - 9-12-2015 at 07:34

Yes, the solvents (and whatever) are getting dumped into the neighborhood and the location of the outside exit vent is very, very important.

Most homes have one or more flue pipes for venting kitchens, bathrooms, and water heaters and even flue-type chimneys (not the old brick towers) and if you can connect the fume hood to one of these that is very good. Then the vent is above roof level, will get any breeze, and be highly diluted before it gets to ground level.

Venting into the sewer line is also a possibility.

You can equip fume events with carbon filters that are readily available in all conceivable sizes due to their universal use in certain types of indoor agricultural operations, and they work well for most purposes. In a typical fume hood airflow is a few hundred CFM and most be appropriately sized.

In my youth at the University of Florida we used to sneak up to the roof of the Chemistry Research Building to watch the fireworks at the annual pre-homecoming game rally for free (tickets always sold out also) in the adjacent stadium. Excellent view. The fume vents were up there also though. We assumed that they would be inactive at that time. Once we got nauseated and inferred that they weren't. I would not recommend doing this.

Yttrium2 - 9-12-2015 at 09:35

Does placing a beaker upside down over a little flask containing solvent prevent more from evaporating, or does it just contain what evaporates? I'm not sure how this would of reduced fumes in the lab if we had to take the beaker off eventually, wouldn't thus cause a lump sum of fumes versus all the flasks slowly emitting fumes?

Any other ideas? What are you guys doing to ventillate? Do you live on an acre, or live in an apartmenr?

Deathunter88 - 9-12-2015 at 09:52

Quote: Originally posted by Yttrium2  
Does placing a beaker upside down over a little flask containing solvent prevent more from evaporating, or does it just contain what evaporates? I'm not sure how this would of reduced fumes in the lab if we had to take the beaker off eventually, wouldn't thus cause a lump sum of fumes versus all the flasks slowly emitting fumes?

Any other ideas? What are you guys doing to ventillate? Do you live on an acre, or live in an apartmenr?


Would you mind telling us what type of solvent(s) you are using? Depending on the solvent used then ventilation may not be absolutely critical.

Edit: Think of this, you have a cup of water that you use to water your plants. You cover it with plastic wrap to prevent evaporation. The next time you lift up the plastic wrap do you instantly see the water level go down? No. So covering solvents with a inverted beaker will slow evaporation.

[Edited on 9-12-2015 by Deathunter88]

ave369 - 9-12-2015 at 10:08

I just open the doors and windows. Recently was cleaning glassware from hexavalent chromium. Found that formalin is a very effective reducing agent against solutions of chromium (VI). But the room was filled with the stinging smell of formaldehyde. I had to resort to the "undog all hatches" treatment.

mayko - 9-12-2015 at 10:32

Quote: Originally posted by careysub  

In my youth at the University of Florida we used to sneak up to the roof of the Chemistry Research Building to watch the fireworks at the annual pre-homecoming game rally for free (tickets always sold out also) in the adjacent stadium. Excellent view. The fume vents were up there also though. We assumed that they would be inactive at that time. Once we got nauseated and inferred that they weren't. I would not recommend doing this.


next time, try a bakery or an italian restaurant; their fumes cause the opposite of nausea... :cool:

Deathunter88 - 9-12-2015 at 16:40

Quote: Originally posted by ave369  
I just open the doors and windows. Recently was cleaning glassware from hexavalent chromium. Found that formalin is a very effective reducing agent against solutions of chromium (VI). But the room was filled with the stinging smell of formaldehyde. I had to resort to the "undog all hatches" treatment.


You realize that formaldehyde is very very toxic. For non-toxic solvents like acetone opening the window is fine. But not for a toxic, carcinogenic compound like formalin. I would go so far to say that the formalin is much more dangerous than hexavalent chromium. (Carc. Cat 2a vs. Carc. Cat 1)

Texium - 9-12-2015 at 16:53

Yeah, it would be a better idea to avoid the formaldehyde in that scenario and just use sodium metabisulfite or a mixture of ethanol and dilute sulfuric acid as your reducing agent.

[Edited on 12-10-2015 by zts16]

gdflp - 9-12-2015 at 17:12

Quote: Originally posted by Deathunter88  

You realize that formaldehyde is very very toxic. For non-toxic solvents like acetone opening the window is fine. But not for a toxic, carcinogenic compound like formalin. I would go so far to say that the formalin is much more dangerous than hexavalent chromium. (Carc. Cat 2a vs. Carc. Cat 1)

The category in which a carcinogen lies gives nearly no information about its potency, it simply is an indication of how much evidence the IARC has that it does indeed induce cancer in humans. An example, wood dust is classified as a Category I carcinogen, whereas N-ethyl-N-nitrosourea is Category II A, yet it is an extremely potent carcinogen unlike wood dust. In fact, it is so reliable, it is used to induce cancer in laboratory animals. Hexavalent chromium compounds are Cat. I along with formaldehyde by the way.

Brom - 9-12-2015 at 19:47

When placing a beaker over a vessel containing a solvent the molecules of the solvent escape or "evaporate" into the void until they reach an equilibrium at which point the molecules are passing into the liquid at the same rate they escape. This is assuming a closed system. Then when you remove the beaker the solvent returns to the state of many more molecules that escape than return.

[Edited on 10-12-2015 by Brom]

Deathunter88 - 10-12-2015 at 05:48

Quote: Originally posted by gdflp  
Quote: Originally posted by Deathunter88  

You realize that formaldehyde is very very toxic. For non-toxic solvents like acetone opening the window is fine. But not for a toxic, carcinogenic compound like formalin. I would go so far to say that the formalin is much more dangerous than hexavalent chromium. (Carc. Cat 2a vs. Carc. Cat 1)

The category in which a carcinogen lies gives nearly no information about its potency, it simply is an indication of how much evidence the IARC has that it does indeed induce cancer in humans. An example, wood dust is classified as a Category I carcinogen, whereas N-ethyl-N-nitrosourea is Category II A, yet it is an extremely potent carcinogen unlike wood dust. In fact, it is so reliable, it is used to induce cancer in laboratory animals. Hexavalent chromium compounds are Cat. I along with formaldehyde by the way.


Yep, 100% agree with the fact the the different categories are based on the amount of evidence the IARC has about whether or not it will cause cancer in humans, not by how potent it is to cause cancer. I too would breath in wood dust all day compared to say ammonium dichromate dust. BUT in this scenario formaldehyde is confirmed to be a very potent carcinogen, and the fact that it is a gas means that you can't just "contain it". ave396 was obviously exposed to WAY more than what is healthy based on the fact that his eyes and nose were stinging. What I am saying is, exposure to the hexavalent chromium solution he was trying to reduce can be 0 if he did not spill it or touch it, yet exposure to formaldehyde cannot be kept to 0 unless a very good fume hood is used.

Also, where did you find that hexavalent chromium is a class I carcinogen? Potassium chromate, dichromate, chromic acid, ammonium dichromate etc. are all class IIa. It would be news to me if hexavalent chromium is a class I...

gdflp - 10-12-2015 at 08:50

Quote: Originally posted by Deathunter88  

Also, where did you find that hexavalent chromium is a class I carcinogen? Potassium chromate, dichromate, chromic acid, ammonium dichromate etc. are all class IIa. It would be news to me if hexavalent chromium is a class I...

See the current list by the IARC.