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Googling these fans, I found some for under $100. These didn't seem to exist a few years ago. I'm now considering building a booth and spraying the best finish, nitro, in my basement. Have any you tried them?

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Hutch

Get the heck off the couch and go build a guitar!!!!

Hutch—

I put down a lot of my thoughts on this topic in this thread:

viewtopic.php?f=10101&t=53585&hilit=Knock+down+spray+booth

A few additional thoughts for you:

First, being explosion proof is not the only feature you need on such a fan. You also need it to have enough horsepower to move a lot of air through obstacles like filters and ductwork. This is where most inexpensive fans fall short. If you give us a link to a specific fan, maybe I and others can be more specific about whether it is a good choice.

Second, any spray booth you design is going to need a fan strong enough to move a high volume of air (as I said above), a hole to the outside world for the fan to send the finish-laden air, and another hole to the outside world to provide make-up air to replace the air being sent out. That last one is sometimes not planned out well enough.

Third, is your basement where the house’s furnace lives? If so, is it a gas furnace? If so, this idea of setting up a spray booth in your basement is very dangerous. Creating a negative pressure air movement system in your basement can mess with the way your gas furnace vents carbon monoxide, and suck it into your living space.

The rest of the dangers should be self-evident, but manageable if you know what you are doing, so I won’t dwell on them. Good luck with your planning.

Watch the ratings - ATEX rated fans, yes, but which Zone?
Gases or Dusts?
What about lighting, switches, are they explosion proof?

Zone Classification for Gases
Zone 0 That part of a hazardous area in which a flammable atmosphere is continually present or present for long periods.
Zone 1 That part of a hazardous area in which a flammable atmosphere is likely to occur in normal operation.
Zone 2 That part of a hazardous area in which a flammable atmosphere is not likely to occur in normal operation and, if it occurs, will exist for a short
period
!A home nitro spraying operation is likely to be Zone 1)

Zone Classification for Dusts
Zone 20 A place in which an explosive atmosphere, in the form of a cloud of combustible dust in air, is present continuously, or for long periods or
frequently for short periods.
Zone 21 A place in which an explosive atmosphere, in the form of a cloud of combustible dust in air, is likely to occur occasionally in normal operation.
Zone 22 A place in which an explosive atmosphere, in the form of a cloud of combustible dust in air, is not likely to occur in normal operation but, if it does
occur, will persist for a short period only.

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The name catgut is confusing. There are two explanations for the mix up.

Catgut is an abbreviation of the word cattle gut. Gut strings are made from sheep or goat intestines, in the past even from horse, mule or donkey intestines.

Otherwise it could be from the word kitgut or kitstring. Kit meant fiddle, not kitten.

In my search for the sub $100 EP fan, I found a number of fans whose description included "Explosion Proof" however, they were not actually rated as described above. Proceed with caution. A local luthier here had his Nitro vapor cloud ignite, almost burning his shop down and burning him as well. Both my furnace and gas water heater are in my basement shop, I abandoned the project.

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Measure Twice,

Karl Borum

Pretty much the feedback above covers everything. I designed a basement booth for spraying waterborne and low(er) VOC materials such as UV cured poly. The make up air is the thing that makes it workable. In my setup I have the fan in a window and then two additional windows on the other side of the space which are opened for make up air. It creates a nice column of air that basically comes in on one side of the house and then exits through the booth.

Here are some videos:

https://youtu.be/H_S4wzRTrd8

https://youtu.be/wwEFVt0tf1g

https://youtube.com/shorts/6dzjbuw-A_A?feature=share

https://youtube.com/shorts/fWPL0orgk3Q?feature=share

https://youtube.com/shorts/4cnSFRa0kPI?feature=share

https://youtube.com/shorts/yFUKnfnlvng?feature=share

Here is a video while in use:

https://youtu.be/o_KLnN-hk5k

Just some feed for thought if you go to tackle it.

Good luck, ymmv, etc…

Brad


Sent from my iPhone using Tapatalk Pro

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To don't use a spray booth to spray nitro in my rundown bungalow workshop. I cover the table saw with a plastic sheet, open the front door and use a large industrial fan to pull the - relatively small amount - of overspray out of the shop. I'm spraying a guitar, not a car. If I succumb to my own stupidity - oh well!
That being said, I wouldn't consider putting a spray booth in my house and spraying volatile chemicals, flammable or otherwise.
For much of the year nitro can be sprayed outdoors if you pick the right days and times, using a simply constructed "spray booth" that will give you 90 percent of the functionality of it's more elaborate cousins.

Explosion proof fans tend to be expensive. But so are hospitable bills, and home repair bills. Take a look at Jenny fans. I think Jegg’s has them. (I was going to mention funeral home bills too, but that just seems excessive)

Ugg! This didn't go well. I'll save my nitro spraying good weather outdoors.

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Hutch

Get the heck off the couch and go build a guitar!!!!

My Jenny, louvers, electronic control was like 1000$. I installed it, then had a pro electrician wire it (sealed conduit). Things 18” if I recall. Plastic blades, sealed motor. It’s a beast weight wise. U just can’t get good explosion proof stuff on the cheap.

you can use induction motor fans I find the ones for HAVC duct fans work well. Been using one for 5 years will soon replace it but they are cheap enough.
The key is no sparks sealed electrical connection.

plan to move the cubic ft of air in the space in a few minutes

My booth is 5 by 7 by 6 I run an 8in 500 cu ft fan and have it double filtered. I also run a 4 in fan at floor level for voc removal

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it

Open frame induction motors can create sparks. I would not advise their use for volatile atmospheres. I use a TEFC motor which is completely sealed. But I am a retired environmental engineer so probably a bit cautious.

I agree. I think in this kind of forum, suggesting anything besides a fan rated "explosion proof" with a good brand name (e.g. Jenny) can possibly be dangerous. Sometimes folks take part of the advice and do something questionable. And then we may bear some responsibility. I mentioned Jeggs above, its actually Summit Racing . Maybe Barry will explain UL Class designations on explosion proof motors (what to look for). Apparently, if it is not explosion proof, it will have no UL listing for Class and Division.

http://www.jennyproducts.com/FanExplosionProof.html (Jenny Motors are UL listed for Class 1, Group D and Class II, Group E, F and G atmospheres)

https://www.masterbond.com/certificatio ... Classified)%20Locations%22.

Mike

I can recommend Dayton tube axial fans (sold by Grainger), driven by a decent electric motor, 1/3 hp and up. These (or comparable substitutes from other good brands) are what commercial open-faced spray booths use to move the right amount of air safely. Expensive, but you can find good deals on used fans, and they are built to hold up, so a used one in good condition would work fine.

You can try to cover all the bases to make a totally safe booth, but some unforeseen failure can occur and make your efforts for naught. That is why I would never suggest someone build a spray booth in their house.
Most Box fans have brushless motors and are generally "non-sparking". You can generate a spark when flipping the switch to turn them on or off, but this is something you want to do before spraying and after the overspray has cleared the box. With a small spray box, open on one side it is doubtful the fumes would be contained enough to create an overpressure and cause an explosion. A vapor cloud flash fire is possible if the fan is not drawing the vapors away fast enough and a spark were to occur to set it off, and might singe your eyebrows if you are unlucky. Again, this assumes you are spraying a relatively small object out of doors.

There is fire prevention, and then there is fire suppression. Commercial booths do both. In my opinion, the most important step a person can take to make a DIY spray booth safe and effective is to be serious about moving the right amount of air. Moving the air well prevents the vapor concentration necessary for ignition to occur. Once you crack that nut, everything else is easier to manage, and I can probably tweak things enough to feel safe. If you fail to crack that nut, the dangers are too high, and I would not try to spray in that environment. Again, just my opinion.

That's a good point, Don. You need both, because having them provides for a comfortable margin of safety. If you only have one you are skating on a razor's edge.

Thanks, Barry. And to springboard from there: Fires and explosions aren't the only dangers to be managed. As I mentioned, I think air handling is the single biggest (but not the only) factor in minimizing fire risks. But it is also the single biggest factor in minimizing the poisoning and respiratory health risks. Some of the chemical we spray are really, really bad for the human body. When we spray finish, we atomize those chemicals and spray them into the air. It is super important to not breath that specific air. Not only do I make air movement the foundation of my spray booth, but I use Mac Daddy PPE. I don't trust regular respirators, because who really fits them properly? Not as many folks as should. I use a PAPR with organic vapor cartridges. Again, expensive, but you can find them used at good prices.

Air flow IN AND OUT is key
also wear a grounding clip on your shoe
As for induction motors creating sparks I have never seen it but anytime you
have electricity yes it may be possible.
the biggest spark creator is friction and static electricity so use metal
and ground it well.
when planning intake air have a fresh air supply coming into the booth, and you want to have it filtered .

keep the booth well sealed so as stated above with fire, you want to be able to starve the fire ASAP.

HEAT FUEL AIR
block one you kill it.

have fun,

one thing if I can pass it along is what you cover your wall with. I used osb but wish I had used the silver backed insulation.

Love the booth , it had helped me be much more productive and it is something I no long have to out source.

_________________
John Hall
blues creek guitars
Authorized CF Martin Repair
Co President of ASIA
You Don't know what you don't know until you know it