Thread: Painting exhaust fan. What do you use?

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In the past I have used box fans, squirrel cage fans, etc for pulling air and fumes out of a space during painting. I know they're not explosion proof, hence this thread. What do you use during painting? I have found a pretty cool way to build a fan to work, but is it all hype? How perfect of conditions do you have to have for the paint particles to catch on fire? Of course I'd rather be safe than sorry and I'm curious.

I did pretty much what you said. I built an insert for the side door on my garage and installed two box fans in it. The box fans have induction motors, so do not spark. Inside the garage, I built a 'spray booth' with 2x4 lumber with Visqueen sides and roof. (sorry, no photos of that) The door to the spray booth had several high-density air filters installed. I opened the garage door slightly for makeup air. The compressor and all other electrics were outside this 'booth.'

I realize this is not 100% safe because the fans are not certified explosion proof, but it's fairly common practice. Check Roger's (rspears) setup on THIS THREAD.

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It takes a pretty heavy concentration of fumes to ignite . I have a booth so mine is outside in the stack . A friend has one if the 36 in fans he bought at tractor supply . He cut a hole in it and mounted the motor outside with a longer belt. Has a piece of 4x4 plywood on it to set in his door .

Ryan, I used something like this, mounted in the gable area of the barn - MaxxAir Heavy-Duty Exhaust Fan with Integrated Shutter, 24 in. Blade | TractorSupply

In theory, I you mount the fan as a pusher, in the clean air indeed, then you should be good. The fan motor could only cause ah ignition if it were placed in the outfeed air path.

Induction motors are not supposed to spark, but the control switch can.

Most of your box fans have open cage motors, it lets the motor run cooler. Explosion proof motors are fully enclosed, and are designed to run hotter

Originally Posted by firebird77clone

In theory, I you mount the fan as a pusher, in the clean air indeed, then you should be good. The fan motor could only cause ah ignition if it were placed in the outfeed air path.

Mounting the fan as a "pusher" creates some challenges with a large bank of inlet filters to keep the dust down without restricting flow. Not that it cannot be done, but exhausting the air is much more efficient, just like pulling air through a radiator works better than pushing.

Thanks for the input guys. I've got to finish a 76 chevy I have to drive this winter and I'm leaning towards painting it instead of just giving it a semi flat paint job. So this led me to start thinking of what to get and prepare for it. Now I have a garage, I'll make a temporary paint booth. In the past I have just swept the walls, ceiling, floor, and put water on the floor. I'd put a box fan in my one window with furnace filters, and on the opposite side had furnace filters in the walk through door. The problem with that is, you'll never get that building perfectly clean, and you can't go out because of the furnace filters. I should have put them on a screen door. Haha Thanks for your input and help guys!

Ryan, when I convert from "shop area" to "paint booth" I hook up the pressure washer and do the walls, inside roof, floors and all. Then once ready to spray I wet down the floors to hold any dust/paint mist down. Just a thought as opposed to sweeping...

The bay walls in my shop I built at my paren's place where I did the painting has two walls tin, two plywood, an dtin ceiling. Not real ideal, but it's what I had to work with. Plus there isn't a water source near the building currently. When I wet the floor down, I'd carry buckets of water and then used a yard sprayer to spray the water on the floor. I was always going to make a temp booth, just never got around to it. I haven't sprayed any complete trucks or cars for a while. Just parts and such lately. That is going to be changing. Hopefully.

I just wanted to add a couple pics from my small home shop. To solve the problem
of air intake I cut a hole in the ceiling, added widow screen to keep bugs out, and
lay filters on top of the joists. (I have a pull down stairwell for access nearby or I
would have a filter rack under the screen.)
[IMG][/IMG]
The attic can get pretty hot without a attic fan to cool it which effects painting. I
try to time my paint jobs for the end of summer when cooler, less bugs, and lower
humidity.
Rich

Here's my exhaust fan which has a sealed motor, and sealed switch. You can see the last paint job was red! LOL It's from Grainger Supply. If I was building a new shop it would be explosion proof.
[IMG][/IMG]
Here's my exhaust hood I installed to keep the neighbors happy. I have taped a sheet to the siding, and wet the ground to catch the exhaust fumes.
[IMG][/IMG]
This gets me by since I do mainly my own projects.
Rich

You can always use a belt driven fan and put the motor in another room or enclosure so only the fan is in the fume path, I myself have painted complete cars with a non enclosed fan, yes I know the risks. I also sprayed lacquer for a living daily at a cabinet shop with a similar fan, it actually took a build up of lacquer and not the fumes to eventually catch fire and it was like 7 years after the fan was installed and we sprayed pretty much 5 days of the week, make sure and keep them blown out as like I mentioned the build up was actually what caught fire and not the fumes!

Just some info....I had a friend who bought my 1970 Z/28. It was sitting in his garage when, at night, the garage exploded and blew the garage door out (it hit his neighbor's house), moved the garage side wall 6" outward, cracked the concrete slab in the garage but did ZERO damage to the Camaro except for minor scorching underneath. Turns out, their lawn mower (Briggs & Stratton) had a leaking gas tank and the fumes filled the floor of the garage until they got thick enough to reach the water heater riser (about 24" high) to set it off. Scary shit. For every flammable, there is an optimum air/fuel ratio that can cause the excitement. A pressure rise of perhaps 1/4 of a PSI doesn't sound like much but a 20' X 8' garage door represents 23,040 square inches. That 1/4PSI rise is really fast and generates almost 6000 lbs on the door.....maybe more if the rise is higher pressure and faster. Blowing up the cheap box fan is not your worry, blowing up the BIG volume of gas inside your garage is the worry. I doesn't take much of a mix if the mix is concentrated in an area. ONE measly box fan isn't enough....look at a professional paint booth, do they use a small box fan? Be safe and make sure your fire insurance is paid up.

I agree on this except for most of us (me included) a professional paint booth is out of price range, use a strong fan and keep the fumes out, a little common since goes a long way. I have done several paint jobs and if your air is really filled with atomized paint your paint job is going to reflect that and you won't get a good slick lay down of your paint also. Size the exhaust fan to the room and crap can the old box fans.
Something to think about, I worked on residential job sites for 26 years, here in MO a painting contractor is hired to spray and finish the wood trim and doors and on new homes the cabinets, 99 percent of this time its done with lacquer (about the most flammable of all finishes) out of the hundreds of houses I personally had been in 1 used a mask, and nearly none where evacuated of fumes. Was it dangerous you bet, is it done? yes daily by countless professionals, a friends cousin was killed by doing this and hitting a drop light which ignited the whole mess. We had a paint booth at work (homemade) and the epa and other agencies are on shops to make sure all this is done according to osha and safely but the majority of violations are done on unpoliced job sites, by the thousands daily, no booth or anything, like I said common since (and insurance) here goes along way...really, if you know how a engine works we all know the risks.

I agree on this except for most of us (me included) a professional paint booth is out of price range, use a strong fan and keep the fumes out, a little common since goes a long way. I have done several paint jobs and if your air is really filled with atomized paint your paint job is going to reflect that and you won't get a good slick lay down of your paint also. Size the exhaust fan to the room and crap can the old box fans.
Something to think about, I worked on residential job sites for 26 years, here in MO a painting contractor is hired to spray and finish the wood trim and doors and on new homes the cabinets, 99 percent of this time its done with lacquer (about the most flammable of all finishes) out of the hundreds of houses I personally had been in 1 used a mask, and nearly none where evacuated of fumes. Was it dangerous you bet, is it done? yes daily by countless professionals, a friends cousin was killed by doing this and hitting a drop light which ignited the whole mess. We had a paint booth at work (homemade) and the epa and other agencies are on shops to make sure all this is done according to osha and safely but the majority of violations are done on unpoliced job sites, by the thousands daily, no booth or anything, like I said common since (and insurance) here goes along way...really, if you know how a engine works we all know the risks.