Paint booth fan?

[Leigh Betsch]

I am converting my downdraft sanding table to a duel purpose downdraft/paint booth. Basically I have a 3'x5' downdraft bench on wheels with an old furnace blower to draw the sanding dust thru the table and out thru furnace filters. With my sander hooked to my Festool dust extractor, it does a fine job. I plan to continue using this for sanding. But, I built a frame over the top of the bench to hang a clean room plastic curtain from and also enclosed the top, thus enclosing the bench. I rarely spray anything but water based finished these days however I think I should build it so I can also spray anything I might need. I would like to mount a separate fan for the paint booth purpose and just use the furnace blower for the sanding downdraft.
Does anyone know of a relatively cheap explosion proof fan for a paint booth?

[Leigh Betsch]

And LED lights, are they paint booth/explosion proof?

[Jim Becker]

I am converting my downdraft sanding table to a duel purpose downdraft/paint booth. Basically I have a 3'x5' downdraft bench on wheels with an old furnace blower to draw the sanding dust thru the table and out thru furnace filters. With my sander hooked to my Festool dust extractor, it does a fine job. I plan to continue using this for sanding. But, I built a frame over the top of the bench to hang a clean room plastic curtain from and also enclosed the top, thus enclosing the sides. I rarely spray anything but water based finished these days however I think I should build it so I can also spray anything I might need. I would like to mount a separate fan for the paint booth purpose and just use the furnace blower for the sanding downdraft.
Does anyone know of a relatively cheap explosion proof fan for a paint booth?

"Cheap" and "Explosion Proof" really have problems being in the same sentence... ;) And I'm serious about that. Unless you believe you truly need to put in provisions for spraying solvent based products, it would be an expensive proposition to build out for that because in addition to the explosion proof fan and the necessary ducting outside (with the negative effect of spilling your heated/cooled air out with it) you'll need to make other safety provisions to isolate the space and do it correctly. With waterborne finishes, you're primary focus is capturing fines in the air from the spraying process which is much easier to deal with. While you still should wear PPE while spraying waterborne, it's primarily for particulates rather than chemical fumes at this point with modern waterborne products.

But if you really want an explosion proof fan, perhaps you can find something surplus rather than buying new.

There should be no issue with LED lighting...it's quite common. Just keep the switch on the outside of the space if you truly need "explosion proof".

[Leigh Betsch]

That's pretty much the same conclusion I have come to but I also thought maybe someone here has an option. I will surely want to do the occasional rattle can of something.
I have found paint booth fans on eBay for about $150 but I'm thinking they are counterfeit and probably not really explosion proof. I plan to just build a duct to mate up with a shop window.





"Cheap" and "Explosion Proof" really have problems being in the same sentence... ;) And I'm serious about that. Unless you believe you truly need to put in provisions for spraying solvent based products, it would be an expensive proposition to build out for that because in addition to the explosion proof fan and the necessary ducting outside (with the negative effect of spilling your heated/cooled air out with it) you'll need to make other safety provisions to isolate the space and do it correctly. With waterborne finishes, you're primary focus is capturing fines in the air from the spraying process which is much easier to deal with. While you still should wear PPE while spraying waterborne, it's primarily for particulates rather than chemical fumes at this point with modern waterborne products.

But if you really want an explosion proof fan, perhaps you can find something surplus rather than buying new.

There should be no issue with LED lighting...it's quite common. Just keep the switch on the outside of the space if you truly need "explosion proof".

[Jim Becker]

I've taken to doing rattle can (solvent based) spraying outside which means avoiding it in the cold months, unfortunately. Even though I plan on a more thoughtful spraying environment in the new shop, it's most likely only going to be suitable for the waterborne stuff I largely spray and I'll just continue with the "outside" thing for rattle cans. But I'm aways from even having that on my radar and I could change my mind. There are some things I'd like to use with my guitar projects that most certainly are not waterborne...

[Rollie Meyers]

Most paint booth lighting is standard fixtures behind wired glass & are accessed from outside the booth.

[Jason Roehl]

If you only spray with an occasional rattle can, you’ll likely never come anywhere near the LEL of the solvent in your spray booth. You may not want to be in there due to the intensity of the fumes, but it takes a specific percentage range of the air to be solvent to even have a risk of an explosion.

[Bobby Robbinett]

We used to spray 100’s (if not more) of gallons of solvent based finishes at work using a primitive wall of the $89 red Harbor Freight exhaust fans. They actually did extremely good. We probably had 10 or more and they were cheap enough and readily available that we could swap one out here and there if one died. Those things last forever in an extremely harsh environment where we abused the crap out of them.

I would build you another down draft table with the furnace blower and just use that as a down draft booth. I am not sure if a furnace blower is explosion proof but I would give it a go or do some research.

I have worked in shops that have paint rooms with 16ft x 12ft walls of fans. My shop uses a down draft booth within an enclosed area. After my work pieces are sprayed they go to a separate room for drying. This is the most ideal way of doing it.

[Frank Pratt]

Haha, 'cheap explosion proof' are mutually exclusive concepts.

You can't use any kind of lighting that isn't approved the location, LED or not. But the work around is easy and one that is very commonly used. Just put a glass panel or two in the top of the booth and have whatever fixture you want sit on top. You do need to seal around the edges of the glass. There are also rules defining how far outside the opening of the booth is also classified as hazardous. I can't provide that for you because I only have the CEC and the NEC rules may vary a bit.

[Jeff Roltgen]

Hey fellow South Dakotan!

How long did it take for Steve Irwin to finally have the death he flirted with for decades?
I am scared sh@@tless that you may actually go forth with improper equipment* as described in another post above. Good for them. They accidentally did not have an accident. Your health, building, and life are simply not worth it. Please, disregard any advice to blissfully go forth doing what you know to be flirting with disaster, just because someone else got away with it.
Damned foolishness.

Just saw the largest commercial cab shop in our region go up in smoke last week. 24,000 square foot building. Opened for business at 7am. By 11:15 the alarm was raised. By 5pm: GONE. Pile of rubble still smoldering 24 hrs later.
No word yet, but chances are it was a finishing room disaster, yet again.

Good grief, people. Share good advice, but keep the daredevil stupidity to yourselves.

*BTW: 10 HF fans @ $89 = enough money to buy a Jenny explosion proof exhaust fan.

[Alan Lightstone]

In my last workshop I bought and installed an explosion proof fan. Moved it to my new workshop for the dedicated finishing room. Wouldn't think of spraying solvent based finishes without it. Nor should you.

Not cheap. Nor is the value of your life.

[Leigh Betsch]

A quick pic of the spray booth as it sets today. I’m still looking for a fan to mount to the back of it. The plan is to just exhaust out the shop window. I’ll make some kind of window sleeve once I get the fan figured out. I plan to make a cabinet into the front, and another one in the end. I installed two LED lights on the sides of the front opening. I have a few areas that need paint also. But for now I’m on hold while I do some work to dust collector. I filled the filters, damn.

[Frank Pratt]

A quick pic of the spray booth as it sets today. I’m still looking for a fan to mount to the back of it. The plan is to just exhaust out the shop window. I’ll make some kind of window sleeve once I get the fan figured out. I plan to make a cabinet into the front, and another one in the end. I installed two LED lights on the sides of the front opening. I have a few areas that need paint also. But for now I’m on hold while I do some work to dust collector. I filled the filters, damn.

You need to move those LED lights along with any associated wiring outside the box. The light can shine through the clear walls. It is not safe to have them inside the booth, LED or not. An added benefit is that the fixtures will not get fouled by overspray.

[Kevin Jenness]

If you are spraying solvent based finishes in any volume you need to decide what level of risk you are willing to take. What you can get away with and what is advisable may be two different things.
Best practice would call for 100 ft/min airflow across the booth area and any possible sparking sources outside the airstream.

I have a 24" tube-axial blower with a (undersized) 2' x 2' filter bank mounted in the wall of my shop. The blower is belt driven so the motor is outside the airflow. You might be able to find a similar unit used.

[Leigh Betsch]

Thanks for the 100 f/min number. It will help a bunch helping to pic a fan. I'd rather not over due it and create a noise monster. If I can't find something reasonably cheap ($150) I'll likely build something. The ebay axial fans I've been looking at are over 2675 cubic meters per hour, and 71db. Compared to the 100 cfm number they are way oversize.

[Kevin Jenness]

Thanks for the 100 f/min number. It will help a bunch helping to pic a fan. I'd rather not over due it and create a noise monster. If I can't find something reasonably cheap ($150) I'll likely build something. The ebay axial fans I've been looking at are over 2675 cubic meters per hour, and 71db. Compared to the 100 cfm number they are way oversize.

The 100 ft/min refers to velocity. If your booth is 5' x 6' (30 sq. ft.) you would need to move 3000cfm through it to meet that goal. Any ducting or filters will increase resistance and require a bigger fan. I assume flow #s quoted are for free air/no resistance.

[Leigh Betsch]

Thanks I missed that the 100 wasn't cubic. My booth is actually 56"x56" and 36" deep. I took a gamble and ordered a cheap eBay fan. It's new and coming from China. It is advertised as explosion proof and 3530 M3/hr. This back calculates to 95 ft/min velocity. A bit short of the 100 but I think it will be ok. I hope it is explosion proof but I don't know if I will be able to tell. $165 plus shipping.

[Michael Schuch]

Would a fan blade mounted on a 3phase induction motor qualify as explosion proof? Or even better, a would TEFC (Totally Enclosed Fan Cooled) 3ph induction motor be explosion proof? Assuming that the motor contactor is no where near the volatile fumes. ...Just thinking out loud more than anything.

[Jim Becker]

Would a fan blade mounted on a 3phase induction motor qualify as explosion proof? Or even better, a would TEFC (Totally Enclosed Fan Cooled) 3ph induction motor be explosion proof? Assuming that the motor contactor is no where near the volatile fumes. ...Just thinking out loud more than anything.

AFAIK, no. With the motor in the air stream...it doesn't matter what kind of motor it is as there can still be "sparking".

[Leigh Betsch]

Here’s a pic of the fan I have on order. I’m hoping it is actually explosion proof as advertised.

[Frank Pratt]

Would a fan blade mounted on a 3phase induction motor qualify as explosion proof? Or even better, a would TEFC (Totally Enclosed Fan Cooled) 3ph induction motor be explosion proof? Assuming that the motor contactor is no where near the volatile fumes. ...Just thinking out loud more than anything.
Nope, not at all.

[Frank Pratt]

Here’s a pic of the fan I have on order. I’m hoping it is actually explosion proof as advertised.
That's a great price. They are cheap enough that you could add a second if it doesn't provide enough airflow.

[Leigh Betsch]

I also made the front curtain short enough so I can reach under it while standing outside the booth. Kinda like a bio glove box. I don’t know how much I’ll actually close the front curtain, but it’s an option.

[Ole Anderson]

Doesn't have to be expensive to be explosion proof. Just Google explosion proof fans, lots of choices under $200. Reminds me that BigAss fans sells a 6 foot diameter shop floor air mover (not explosion proof) for $7k. There is a price point for most any market. https://www.amgair.com/big-ass-fans-6-5-ft-black-jack-portable-fan.html

[Derek Meyer]

BigAss Fans are awesome. We have 3 of them in our store that run at low speed 24/7. They've been running continuously for 7 years now and none have had an issues whatsoever. They are expensive, but I think they are worth every penny.

[Rob Luter]

I'm seeing a great deal of ignorance on what "explosion proof" really means. The reality is it can mean a number of things depending on the risk level. It means different things depending on whether you're dealing with liquids, gasses, or dust. The NFPA is a great source of information on the subject. If you want to go whole hog, design to Class 1, Division 1. Everything sealed, no possibility of sparks, no possibility of static discharge, etc.. Note that this is crazy expensive and nothing you need unless you're processing fuel or running a munitions depot.

To the OP: Please do some research. The fan you depict isn't explosion proof. If it was the impeller would be bronze and the motor would be both TEFC and out of the airstream. That said, I think you'll find that your proposed solution will be just fine given your stated scenario. Make sure you move plenty of air so the concentration of any fumes doesn't reach an explosive level.

[Frank Pratt]

I'm seeing a great deal of ignorance on what "explosion proof" really means. The reality is it can mean a number of things depending on the risk level. It means different things depending on whether you're dealing with liquids, gasses, or dust. The NFPA is a great source of information on the subject. If you want to go whole hog, design to Class 1, Division 1. Everything sealed, no possibility of sparks, no possibility of static discharge, etc.. Note that this is crazy expensive and nothing you need unless you're processing fuel or running a munitions depot.

To the OP: Please do some research. The fan you depict isn't explosion proof. If it was the impeller would be bronze and the motor would be both TEFC and out of the airstream. That said, I think you'll find that your proposed solution will be just fine given your stated scenario. Make sure you move plenty of air so the concentration of any fumes doesn't reach an explosive level.

Good catch on the fan Rob. I thought it seemed too cheap. Now that I think about it, just the termination cost to an explosion proof motor could easily more than double the price of that fan. That would include labor because that is not a DIY thing.

The inside of the spray booth is Class I, Div I. Explosive concentrations of vapors will routinely happen there. Hence my strong suggestion (if I could insist then I would) that the LED lights be moved outside the booth.

[Alan Lightstone]

I'm seeing a great deal of ignorance on what "explosion proof" really means. The reality is it can mean a number of things depending on the risk level. It means different things depending on whether you're dealing with liquids, gasses, or dust. The NFPA is a great source of information on the subject. If you want to go whole hog, design to Class 1, Division 1. Everything sealed, no possibility of sparks, no possibility of static discharge, etc.. Note that this is crazy expensive and nothing you need unless you're processing fuel or running a munitions depot.

To the OP: Please do some research. The fan you depict isn't explosion proof. If it was the impeller would be bronze and the motor would be both TEFC and out of the airstream. That said, I think you'll find that your proposed solution will be just fine given your stated scenario. Make sure you move plenty of air so the concentration of any fumes doesn't reach an explosive level.

Why bronze impellers vs steel? I've seen aluminum suggested as well. Because they won't spark vs steel??

[Alan Lightstone]

I found this link which seems to go into detail regarding the NFPA 33 Spray Booth Regulations. Interesting, but TL;DR parts of it.

https://www.spraysystems.com/nfpa-33/

[Leigh Betsch]

I’ve pretty much concluded that I’ll stick to water base finished with an occasional rattle can of something. The fan is supposed to flow 2077 cfm which will give me 33 air exchanges per minute. I’m pretty sure this will be more than adequate for any rattle can work I’ll do.

[Rob Luter]

Why bronze impellers vs steel? I've seen aluminum suggested as well. Because they won't spark vs steel??

Yes. Exactly.

[Rob Luter]

I’ve pretty much concluded that I’ll stick to water base finished with an occasional rattle can of something. The fan is supposed to flow 2077 cfm which will give me 33 air exchanges per minute. I’m pretty sure this will be more than adequate for any rattle can work I’ll do.


An air change every 2 seconds will deal with anything you could spray at it.

[Leigh Betsch]

So how did this all work out you might ask.

Just excellent. I built a plenum withe cheapo furnace filters to catch most of the overspray before it gets to the fan. There is plenty of airflow but not so much that it effects the spray pattern. The pic is of the initial run. I sprayed some molding with Target EM6000 that I dyed black. You can see in the pic that the filters catch the overspray. I need to build a couple of fixtures to hold my parts while spraying instead of the paint cans and put a couple of overhead pipes to hang things from. But overall I’m very happy. The fan pulls all smell and shoots it out the window. And I didn’t blow myself up! Of course this was a water base finish.