Using a standard (not explosion safe) pipe fan for IPA steam?


I am a bit wooried about possible IPA, that may evaporate out of my Form Wash. So before I use the machine, I want to build a box (wood) and place the Form Wash inside. Then I would like to suck the IPA steam with a pipe fan out of the box and blow it outside the window. But I am unable to find any explosive safety pipe fan, that is cheap enough (<200 Euro). Therefor I would like to ask, if you have any experience or recommendations how to deal with the IPA steam. Can the concentration be high enough to cause an explosion by using a standard pipe fan? Thanks.

There should be no steam.

That said I wouldn’t use anything other than an explosion proof fan in an enclosed system that has flammables in it.

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There are two ways to vent a box-
one- a duct with an axial fan inline sucking the air out.

the other is TWO ducts… one leading out, and the other with an axial fan blowing IN. Create positive air pressure inside the enclosure with only one- very low resistance path for air to escape.

The in blowing solution does not allow the electrical components of the fan to come into contact with flammable vapors. There should be a flap valve between the fan and the box so that air CAN NOT flow the other way- like when you open the cabinet door.


Probably a bad idea to confine a flammable vapor with a fan that is not explosion proof.

The actual risk depends a lot on how diluted your IPA is. If you are using 70/30 (IPA/water) then the odds of something igniting are pretty low. If you are using 99% IPA that’s another story.

You can also use a carbon filter to drop your risk even more, though that will create a pressure that your blower will have to work against.

Is the top of the formwash flat?

I’m just thinking that it would not be that hard to make a custom silicone blanket- 1/8" thick- that would fit the contour of the top of the Formwash and essentially seal the gaps that allow vapor to escape…

Just that, and it being in a box with some activated charcoal filters like those for composters should eliminate any venting.

What I don’t like about the box with fan idea is that the higher the unsaturated airflow around the formwash- the faster the IPA is going to evaporate.
A week between prints could cost you a gallon of IPA just to evaporation.

A silicone “cap” would have to cover the entire top and wrap around the upper edge of the Formwash with about a 1" overhang. Cast to be slightly smaller than the Formwash- so that it would fit tight around the bezel BELOW the crevices and gaps in the lid hinge and protruding bucket lip- enabling it to seal agasint the smooth surface of the bezel just below these complications. Yeah- it would be like a Tupperware lid you had to snap off and then back on when you used the formwash- but it would prevent loss of IPA and having fumes fill your office space…

If anybody here has a formwash in San Diego country or nearby that I can take a scan of- I can make the tooling for producing these kinds of gaskets.

Or- maybe Formlabs has a 3D model of the Formwash that would work?

I think I will come up with some own fan construction, where all electric parts are far away and outside of the box. And I will put some kind of gasket on the Form Wash.

be careful. IPA at 99% can build a concentration of fumes… and no matter how far away the fan… the fumes have to pass thru the impellers of the fan and that impeller is connected to a motor that can spark.

If you are going for a gasket- You do not NEED an evacuated cabinet for storing the formwash.
Any standard exhaust hood will do if you are only turning it on when you are cleaning parts… because an exhaust hood would be diluting the fumes with room air the entire time you are running it…

The gasket would prevent evaporation when the unit was not in use.

The lid of the FormWash is complicated enough to make lid gaskets untenable… but as described above- you could make a tool to cast a silicone rubber “Cap” that would stretch over the whole top of the Formwash and cover a full top inch or so… like a tupperware lid.

I will only use 90% IPA. Furthermore the motor will be attached to the fan-impeller with a long axle and with suitable isolation bearings between. That way, the fumes will never actually pass the motor. There should not be any possiblity for a spark to get inside the box with fumes.

I think the box itself should be not too small for IPA fume concentration issues and not be fully isolated against the outside, because otherwise there could not get fresh air inside the box.

Also the “tupperware” gasket seems important. Does anybody know how the motor inside the Form Wash is isolated from fumes?

It will be a brushless DC motor. No commutator, no chance of a spark.

The Form wash is a magnetically coupled stirrer like most lab equipment. You can actually lift the bucket/tank off of the rest of the machine to change out the IPA.

I think this may be an excessive level of concern. We have one of these in an office environment for 6 months now and you never even smell the IPA unless the tray has just lifted out and everything is still wet.

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