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Author: Subject: Resistance of PVC tubing to common ether vapors
p4rtridg3
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sad.gif posted on 29-11-2020 at 11:58
Resistance of PVC tubing to common ether vapors


I'm almost finished building my amateur fume hood (wood construction, with brushless motor exhaust fan) , and I chose a flexible pipe made of fairly thin PVC to carry the air out of the fume hood and outside. I chose PVC because it is generally regarded to be one of the more chemical resistant plastics, and it's still cheap.

However, I will be using ethers in my fume hood, including toxic ones like 1,4-Dioxane. PVC is generally considered to have poor resistance to ethers and ketones. Since it will just be vapors, in low concentrations, and moving quite quickly with the airflow, will it really matter? I want to be sure that above all else, they won't seep through the PVC and enter the room air.
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macckone
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[*] posted on 29-11-2020 at 12:43


Ether is incompatible with PVC. You say it is thin so I would expect rapid deterioration.
You also need to keep the ether fumes below the explosive limit.
That limit is 2%.

If it is multilayer ducting then you should be good.
But you need to inspect it for deterioration.
No ducting material is perfect.

Example:
https://www.amazon.com/Homend-Flexible-Ducting-Ventilation-K...

PTFE lined ducting is awesome but expensive as hell.
http://www.acehose.com/1duct.html

The insulation on the coil windings may also be adversely impacted as there is no way of knowing what the actual coating is.
If the fan motor is out of the air flow that it is all good.

If you are making your own ductwork, 1/8" hardboard (high density fiberboard) coated with epoxy paint is relatively cheap and will survive almost anything.

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Deathunter88
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[*] posted on 29-11-2020 at 21:43


I disagree with macckone. By the time any vapors get to the duct it should be sufficiently dilute to not cause problems. I used a very thin aluminum duct (think foil-like) working with dense clouds of sulfuric, nitric, hydrochloric acids along with copious NO2 and Br2 vapors for many years with zero deterioration.
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macckone
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[*] posted on 30-11-2020 at 02:10


deathhunter,
PVC != Aluminum

PVC will act like a sponge for solvents.
Even at low levels.

Most aluminum ducting is mylar coated to reduce corrosion.

Really old uncoated aluminum ducting will literally fall apart just from heat and moisture.

PET is pretty resistant to acids, bases not so much.
But the aluminum will prevent failure unlike the straight PVC stuff which is really intended for moist air, not solvents.
The multi layer ducting is PET/Aluminum/PVC with PET being on the inside.
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