DIY spray booth fan/blower advice

[nuno81291]

Hey TRW, I am looking to build a small booth to complete painting projects without being subject to the weather (and winter). I see Dayton blowers are highly regarded. I however have access to a unit that is an in-line 400cfm exhaust fan (active air by hydro farm). I am sure I could get away with spraying acrylics but how about using rustoleim/Krylon spray bombs? I have a large stash of these that I use all over the layout and would hate to have to get into airbrushing and the associated costs. Should I not consider using spraybombs with any of the DIY plans? Seems a lot say you would be unlikely to hit the LEL but I must admit it gives me pause.

[Lemosteam]

Timely.  I am about to make one tonight as well. I have heard that a sealed coreless fan will work in that environment.

Mine is a 12v double 4" fan housing from a tower heater that failed, but they still work. They look very similar to computer fans. I am hoping that I will not have issues too.

[Philip H]

So it’s all about volume sprayed versus explosive chemistry. Most hobby paints sprayed at our usua do illutions aren’t anywhere near concentrated enough to explode if you spark. That said eliminating spark sources is always a good idea. Which is to say if the Dayton is sealed then you should be fine.

[peteski]

What type of a motor does that 400 cfm unit have?  While it is highly recommended to have the motor out of the air-stream when using flammable paints, many 120V AC fans and blowers use AC induction motors which have no brushes or any other sources of sparks and should be relatively safe.

[rodsup9000]

  While it is highly recommended to have the motor out of the air-stream when using flammable paints,

 I'm using a 4" boat bilge blower on mine and has worked for years. And they are cheap and designed for combustible air ventilation. Get them at Bass Pro, Cabela's or your local boat dealer or on the net. One drawback is that that there are 12 volts.   

[ednadolski]

If you're going to use spray cans then you probably want a +1000 or so CFM blower.  I stuck one on my spray booth and it's worked out really well.  Yes it costs more but there is a safety factor too (you might be surprised at just how much those cans can throw back at you, esp. in a smaller space).

Ed

[narrowminded]

I discovered this a couple of years ago while researching parts to build my own.  Doing some arithmetic I decided to buy it.  There are many like this but the exhaust duct pieces to go out the window and especially the very bright LED lights in the booth are not offered on every one.  This one has them.  I've been totally happy with it.    Low noise, well built, compact and easy to close up and takes little space when stored.  Very clever and effective design.   For $72.50 shipped and ready to run with ducting and all the incidentals done, I decided I couldn't do better on my own.

Spraying acrylics I don't worry about running the exhaust outside and get no discernible odors.  With solvent based you definitely want it ducted out.   I used some scrap foam pieces to make an insert piece that fits the window frame and holds the furnished exhaust duct piece when needed.  A few inches high and just inserted and clamped by closing the window on it.  That keeps the weather and fumes out while in use.

https://www.ebay.com/itm/Portable-Hobby-Airbrush-Paint-Spray-Booth-Kit-Exhaust-Filter-LED-Light-Set-Model/192041375026?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D20131003132420%26meid%3D125f93952fae4e898041773b7ece482d%26pid%3D100005%26rk%3D3%26rkt%3D11%26mehot%3Dpp%26sd%3D263994437476%26itm%3D192041375026&_trksid=p2047675.c100005.m1851

[nuno81291]

If you're going to use spray cans then you probably want a +1000 or so CFM blower.  I stuck one on my spray booth and it's worked out really well.  Yes it costs more but there is a safety factor too (you might be surprised at just how much those cans can throw back at you, esp. in a smaller space).

Ed

Wow I wouldnt have thought that high of CFM necessary. I use these to vent/exhaust 1000w HID lighting and have them on a dimmer generally quite low such as 20%. Feels like a mini hurricane when you run them full speed. 

Pete- how would I be able to tell if it is a brushless motor? I find nothing on a product spec sheet, other than warning against use in a flammable environment (which it seems  like the regular Dayton blowers advise against).

I am not against purchasing the actual booth, mostly wanted to slap it together since I have a surplus of ply on hand and tools from my past life contracting. Then again all I would need is a light and filter and ducting since I would have to build a window adapter.

Perhaps I should start looking into airbrushing acrylics. I have no affinity for the solvent paints, other than having a long collection of them. I certainly like the idea of the control of an airbrush... time to start counting pennies I suppose.

[Philip H]

So the issue here is not one of chemistry or air movement but legal liability. 400 CFm properly vented will in all likelihood get rid of solvent paint fumes from airbrush use and most spray bombs without causing an explosion hazard because the volume of fumes (and thus concentration) is really low compared to the volume of air moved. In other words you have to spray a lot of Scale coat or floquilnfof a long time to get the fume concentration up to where it might explode if you started the motor (which is really where the spark hazard is).

Dayton doesn’t want to tell you this because their lawyers are concerned that if you even think these thoughts you will sue them for an unsafe product.

[peteski]

Pete- how would I be able to tell if it is a brushless motor? I find nothing on a product spec sheet, other than warning against use in a flammable environment (which it seems  like the regular Dayton blowers advise against).

Majority of fan motors running from 120V AC are induction motors.  These have no permanent magnets, the coils are always wound on the stator and the rotor is a solid chunk of metal (made up from iron and aluminum (no typical copper wire winding you would see in other motors). These motors do not have a commutator or brushes.  The solid metal rotor and lack of a commutator are the biggest clues for identifying an induction motor.  If you can peek inside the motor, you can easily tell what type of a motor it is.

If you go to Google and search images for induction motor you will see examples of what they look like.

[ednadolski]

Wow I wouldnt have thought that high of CFM necessary.

There are formulas for calculating CFMs based on the open area of the booth.  That being said, what is "necessary" depends on a lot of factors.  I get rather uneasy about the amount of blowback that those spray cans can generate in a confined space, so I like to have enough draft that e.g. will at least have a slight 'pull' on a candle flame.

@Philip H has a point, in that mfr. specs are (necessarily) tied to specific uses. So rather than sifting thru stacks of OSHA specs or whatever, and trying to decide what is or isn't applicable, this is one of those situations where some 'overkill' isn't necessarily a bad thing. (JMHO )

Ed

[daniel_leavitt2000]

I use a US Postal sorting box (the white plastic thing). I set it on its side, added three high performance "Slot Fans" for gaming PCs in the back with the exhaust vents blowing though a hole cut in the top. I then added a few lines of rope LEDs for lighting, all attached to a 12v, 2 amp power supply.

When I'm ready to spray, I put a 12x12 air vent filter in front of the fans.

This works well for acrylics - especially non toxic ones like Model Flex and Tamiya. With laqucer based paints I would recommend a mask unless you have the exhaust piped to the outside.

I have run direct alcohol and lacquer thinner into the fans to see what would happen. No fire, no boom.

[tom mann]

I would think for anything that’s not acrylic coming out of the airbrush you need a solution to vent outside.

[peteski]

I set it on its side, added three high performance "Slot Fans" for gaming PCs in the back with the exhaust vents blowing though a hole cut in the top. I then added a few lines of rope LEDs for lighting, all attached to a 12v, 2 amp power supply.

I have run direct alcohol and lacquer thinner into the fans to see what would happen. No fire, no boom.

The personal computer cooling fans use brushless DC motors. Most air-moving fans in fact use motors which are either AC induction motors or DC brushless motors. No brushes - no arcing.  There might be some larger industrial fans/blowers which use motors with brushes, but that is likely rare. Even the large fans and blowers usually utilize AC induction motors.

[narrowminded]

For what it's worth, one way that this gets done safely on a larger industrial basis is to have the motor isolated outside the duct, driving the fan with a belt and pulley that penetrates the duct wall enclosed in a tube that also carries the fan shaft bearings.  This was how my booth was built in my place when I worked for a living.   Here's a 3D example of the manner of construction: https://www.grainger.com/product/DAYTON-12-Tubeaxial-Fan-4C659