# Diy vent hood advice



## Xydoman (Jul 16, 2021)

Hello again yall. So I have a good one for you this morning. I'll get right into it: I'm going to start building a fume hood today, and I'm what you would call an extremely avid DIY-er as well as a excellent "sourc-er", for lack of a better term. In other words, I can build marvelous machines and contraptions ( alot of times with hardly any money, due to connections I've made in the construction industry, and my particular role there, which alot of times puts me on a given jobsite as they're nearly finished, and throwing real good material in the dumpster to clear it out. Anyways, I've got my material, and I've got a brand new fan with a brand new motor, that was going to go on a small boiler, but was scrapped due to an ordering mistake, and subsequently, given to me. Part of my job happens to be sizing components to move determined quantities of air, so I kno the fan will work, but there's a problem here.. It's made of steel and aluminum. I have a few ideas on how to protect the motor from the fumes by building a sealed housing, allowing the fan to protrude into the ductwork. But my problem is with the fan and tge shaft. All of that, to get here.. To my question.. Is there something I can coat, or spray the fan down with to protect it? Some sort of.. Idk.. Plastic coating?? Rhino liner, varnish? Flex seal?? The reason I need yalls advice is because I'm not too knowledgeable in the area of what's safe to mix with what. And as such am unsure of tge reactivity of such protectant with the chemicals I'll be using. . So I stick to a few key processes in this gold recovery endeavor, and I only deviate from said processes after much research and advice from this forum. So basically just hcl, nitric acid, and the 2 combined. Thank yall. Happy Friday!


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## rickbb (Jul 16, 2021)

Take the fan apart as far as practicable and spray paint the insides, (the parts that are exposed to the fumes anyway). Any good paint will work, doesn't have to be special paint. 

This will add some protection and make the fan last longer than without painting. BUT, it will not protect it forever. I have a cheap blower fan I'm using and painted it this way and it's been 5 years or so and no large rust problems yet.


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## Xydoman (Jul 20, 2021)

Hmm.. Simply spray painting it?? That's easy enough. I appreciate it.


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## nickvc (Jul 21, 2021)

The other option is to reverse the fan to a blower and create a Venturi that will keep the fan from the worst fumes, a bit more complicated but it can and has been done many times.


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## Xydoman (Aug 20, 2021)

Interesting. I'm familiar with the venturi principle. Many gas burners use this effect to mix air into fuel used for combustion.


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## jadedalex (Nov 4, 2021)

You also might try using a coupling to attach a long shaft with fan blades into the hood enclosure thus keeping your motor out of the hood. Another avenue is to use a leaf blower that blows into a duct with the top of your fume hood attaching to the ducting at a 45 degree angle. This creates the Venturi effect that NicV spoke of. I'd still spray the hood and fan blades with Teflon spray cuz Teflon is impervious to acid fumes...


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## UncleRicky (Nov 11, 2021)

I used a blower designed for greenhouses, attached a sanitary “T” (more like a “Y”) to the output end with the blower outside of the building, and just the “T” inside the fume hood. This way no fumes go through the blower but are sucked up in the Venturi affect. Velocity is not optimal but I feel that adding a length of straight pvc to the “T” will increase velocity…just haven’t needed to do that yet as I process small batches.


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## Noggin (Nov 11, 2021)

I installed a duct boost fan that’s variable speed right at my outside vent so that only one joint can fail and push fumes into my shop. I mount the controller right on my hood so I can keep it on low when not in use or high when making something really nasty. I love the setup. 
And moving air through there 100 percent of the time has not seemed to let anything corrode. The fan is mostly plastic. I took it apart for inspection a couple days ago. 
If your current setup fails in the future, this might be something to try.


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## 4metals (Nov 11, 2021)

Go to the library section and there is a thread there on doing exactly what you are asking. Making a hood with a plain steel blower.


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## Arthur Brown (Nov 21, 2021)

The proper answer is a bifurcated fan, one with the motor out of the airstream.


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