DIY Airbrush Paint Booth – Help me Select a Blower Fan

48 Comments

1. Anson

   Oct 16, 2022

   Local town ordinances may have rules about venting untreated paint booth air outside.

   If you thin with alcohol/spirits/etc please use a p100 with vapor cartridge. Some acrylic airbrush mediums are flammable when the paint is not.

   If acrylic and latex are ALL you’ll ever use in the paint booth you could use a dust collector for suction and put the money to multiple or better filters. Personally I can’t, too easy to “Just this one time” and regret it.

   Reply

   • Stuart

     Oct 17, 2022

     Good point, thank you!

     I’ve read about guidelines for things like auto paint booths before, and the last time I checked there was nothing about hobby grade or low volume acrylics.

     The two acrylics brands I would use are non-flammable, and the mediums and related fluids say the same.

     I also like the idea of a hobby tool dust chamber.

     Maybe I could have blast gates and an easy filter removal that allows for swapping between overspray filter and sawdust hood that’s connected to my dust extractor, but I’m not up to thinking that through yet.

     My main reason for entertaining the idea of exhausting out a window is to better control the air flow.

     Reply

2. Pietro

   Oct 17, 2022

   [More airflow usually means more noise, not necessarily just from a motor, but from the air movement. But more airflow means greater air speed,] – Ussually it is true but dont have to folllow that stament. Same amount of 400CFM of Air flowing tru 4″ tube vs 12″ X 24″, bigger area would have slower air movement but same volume. Properly desingned fan with larger diameter can have higher airflow and less noise. Tiny fan would have to spin more(while creating more noise from blades) in order to match same flow. Just think of window fan vs BIGASS fans in the warehouse.

   My recomendation is to go with furnace blower (have seen it used for sanding table to pull down dust) since regular filters can be used and you can adjust blower speed with pulley swap. You only need ″explosion proof or intrinsically safe motor″ when motor is exposed to flamible/cumbustible gas. Motor can be mounted or caged in box, to keep quiet and away from spray.

   Reply

   • Stuart

     Oct 17, 2022

     But which size or motor style?

     The one recommended by the DIY parts company appears to be lower spec’ed than comparably-priced blowers or similar size.

     265 CFM, 2A draw, sleeve bearing, and 1610 RPM vs 273 CFM, 0.8A draw, ball bearing, and 1640 RPM.

     Grainger says the first model is made in USA, but these things change often. That model doesn’t appear into be catalog, with both that model and the one I am comparing it to here being listed as replacements for a third model.

     The other furnace-style blower, also spec’ed above, is a little bigger and delivers a lot more air.

     It feels like I’m missing something here.

     With a larger fan, I could potentially have separate filters, such as a more easily replaced pre-filter.

     Reply

3. Daniel L.

   Oct 17, 2022

   HVAC mechanic here. Happy to help.

   *What’s the downside of a motor consuming less power to put out the same air volume?*

   There is none, although a lower amp draw in an AC motor doesnt necessarily mean less power consumed.

   The reason? Power factor. Shaded pole motors are typically abysmally bad in terms of power factor. This has to do with the way inductive motors (and loads) shift the current and voltage waveforms out of phase with each other.

   What does that mean? The peaks of the current waveform will not occur simultaneously with the peaks of the voltage waveform. Maximum voltage pressure does not align with maximum current flow.

   Because we know that at its most basic level. Watts law is VoltsxAmps=Power, we can see how this affects the way having these waveforms out of phase with each other will affect the total power consumed:

   Example (simplified) load: 100Vac applied, the load pulls 10 amps. BUT, the peak of that 100Vac waveform occurs at a time when the current waveform is rising and has not peaked yet. Let’s say that, at the instant thay the voltage waveform peaks, the current waveform is only at 8 amps.

   Well, 100Vacx8A=800 watts. But that’s just a snapshot and is really only useful for illustrating how power factor affects power consumption. Our example motor here would have a power factor of 0.8, which is pretty good, and near what some well designed 3 phase AC inductive motors can do. You’d likely never see a power factor like that in a single phase motor.

   We see that in the above example that our measured current and voltage would seem to imply that the fan is using 1000 watts, but because the current and voltage waveforms are misaligned (out of phase) that the motor is only actually using 800 watts.

   But…here’s the rub. Both the apparent power (Volt Amperes, or VA) AND the REAL power (watts) are useful figures, determined by the following two equations for single phase AC inductive loads:

   Volts X Amps = VA (apparent power)

   Volts X Amps x Power Factor=Watts (actual power)

   VA is the number you must use for engineering everything that electrically feeds the motor. The transformer, wire, and all other accessories will “see” VA and must be rated for the RMS amp draw and voltage of the load being supplied. This is why power factor becomes a big deal in larger motors: a small shift in the power factor of a motor can have huge implications for the cost of the electrical infrastructure surrounding the motor.

   With a power factor of 0.5 (not uncommon for shaded pole motors), suddenly that example above required an infrastructure capable of serving a 1000 watt load, but you’re only *really* using 500 watts. Less power used=less work done.

   Now…that’s just considering the actual amount of power used vs. how much is actually used. That doesn’t have anything to do with efficiency, which is how mich of the power being used is actually converted into mechanical energy instead of heat…another area where shaded pole motors don’t do well.

   PSC’s are a time-tested and rock-solid design, and they use a capacitor to help shift the current and voltage waveforms a bit closer together, which leads to better power factor and increased torque.

   For a setup where you’re loading up a filter with particulates and increasing the static drop across the filter over time, a PSC will typically cope a bit better than a shaded pole motor. That said…there are other considerations, not the least being the fan wheel and the actual TESP the assembly is rated for. You seem to have a pretty good handle on the basics there.

   Keep in mind, I’m just a mechanic writing a long post when I really should be trying to sleep, so I might have a few things kinda askew here. I’ll read through a bit more tomorrow and see if I can add anything else of use. Not that power factor is really all that useful…just been one of my favorite things to talk about with my apprentices recently.

   Reply

   • Stuart

     Oct 17, 2022

     That makes a lot of sense – thank you!

     Right now I’m just guessing at static pressure drop values, but I see there are some filters that come with specific ratings at set fpms, which helps a bit.

     Reply

   • Nathan

     Oct 17, 2022

     Thanks for that saved me a bit. But I was going to shorten it to – one big issue is that fan and motor combo is rated to a range. you get outside of that and you can have issues where the flow won’t be consistent or the motor will burn out early.

     Reply

4. Bruce

   Oct 17, 2022

   I’ve actually used the Dayton fan you’ve pointed out as well as the Soler. The either will move enough air for your small spray booth. The Soler is easier to package and a lot quieter. I’d pick the Soler if I was building it. Slightly oversize your cfm and use a speed controller if it’s too much. As long as you don’t go overboard on your filtration, the static pressure drop will be very low in this application. If you are exhausting out of the building, you’ll need to open a window to allow for make-up air.

   Reply

   • Stuart

     Oct 17, 2022

     Which Dayton (if you can recall)?

     Vent Works recommended 6FHX9 .

     1TDR7 is a larger blower spec’ed at moving more air.
     1TDR3 has a slightly smaller and larger wheel than the X9, and delivers comparable air at much lower power draw.

     Reply

5. Daniel L.

   Oct 17, 2022

   *More airflow usually means more noise, not necessarily just from a motor, but from the air movement. But more airflow means greater air speed, which means more particulates pulled towards and captured by the filter.

   Right?*

   To a certain extent, yes. The biggest issue you’ll be up against here is the pressure drop across the filter. More CFM=higher FPM when all other factors remain the same. Higher FPM=a greater pressure differential across the filter if all other factors remain the same.

   As a general rule of thumb, its good to keep Filter Face Velocity (FFV) between 250 and 500 FPM. This comes down to a matter of CFM/area=FPM. Pleated filters have a distinct advantage here, as the pleats effectively increase the surface area of the filter.

   That said, I’ve done a paint booth for a company in the area that used to have a name that rhymes with “maceshook” that used simple media filters. Sorta like big scotch bright pads. Granted, that was a big walk-in deal in which they weren’t hurting for workshop space…

   Anywho, should you find that your filter face velocity is getting a bit too high, you can offset that by increasing the thickness of your pleated filter. This will reduce the pressure drop across the filter, and will help keep your motor and fan assembly operating healthily (excessive static not only strains the motor, but also the fan wheel assembly).

   Another upshot- if you design for thicker filters, your filter opening does not need to be as large to accomidate the same FFV. While thicker filters generally aren’t available at home depot and the like, they’re easily found online.

   The minimum size of the particulates you’re looking to filter out here will determine the rating of the filter you’ll want to use.

   Butttt…now I gotta go to work. Yeesh. Will read more later.

   Reply

   • Stuart

     Oct 17, 2022

     Thank you!

     I’m trying to understand filter selection as well.

     There’s paint collector air filter rolls (https://www.grainger.com/product/AIR-HANDLER-Air-Filter-Roll-26-in-Nominal-2EKK4) with 1″ thick polyester (or fiberglass depending on model) filtration.

     The resistance seems high – 0.19 at 300 fpm and 0.32 at 500 fpm. From my understanding, this value will be lower for lower fpm.

     With a frame, I could custom-cut filters for at or less than $2/each.

     But would standard HVAC pleated filters be better? They’re thinner, and so I would think collected air takes a shorter path with fewer contact surfaces to capture paint, but the pleats increase the apparent surface area to help reduce the pressure drop.

     There’s also the question about whether both types of filters would work well or be overdoing it.

     MERV 5 fiberglass filter vs MERV 7 polyester?

     Merv 7 polyester + home HVAC MERV 11 (or similar) 3/4″ thick pleated air filter for any fine particulates?

     Interestingly, the smaller consumer models all seem to have separate blue and white filtration pads. https://amzn.to/3yHM98z

     It seems that a thick paint filter will help collect overspray with less clogging than a finer filter, but a finer filter will help collect smaller particles from circulating into the air or exhaust.

     And just to ensure I’m understanding things correctly (thank you again!), 250 to 500 fpm is the filter face velocity, but how does that correlate to the box-opening air speed?

     FFV = CFM(taking into account any other drops such as in ducting) / filter size

     Opening velocity = CFM after filter (taking into calculated or measured static pressure drop) / opening cross section ??

     As I understand it, the static pressure drop of a filter, and its effect on the CFM reduction, is dependent on the the FFV and filter properties.

     So for a filter rated at 0.19 at 300 fpm and 0.32 at 500 fpm , I can use that and blower fan spec charts to determine approximate in-system CFM properties for a particular filter or combination.

     For the 1TDR7 filter listed above, with 485 CFM at 0″ SP, 448 CFM at 0.2″ SP (from the blower’s full spec chart), and 375 CFM at 0.5″ SP, and taking the 300 fpm I would be able to predict approximately for a 12″ x 24″ filter:

     485/2 = 242 fpm FFV, 448 CPM and 224 fpm after a clean filter, and 375 CFM and 187 fpm when the filter is recommended to change at 0.5″ SP.

     In theory, the opening size would then be 375 CFM/100 fpm desired = 3.75 square feet. So my opening could be as large as 30″ x 18″ and still achieve the desired air speed up until a filter change is required, with SP usually measured by differential manometer.

     For trapezoidal openings, would the cross sectional area be the rectangular working width x height, or exact measurements of the angled dimensions?

     And does the working depth have any reasonable influencer on air speed or filtration efficiency, or is it only needed when calculated air exchange rates and similar?

     Reply

     • ToolGuyDan

       Oct 17, 2022

       I believe Daniel’s point is that something like a 12x24x4 filter will be substantially better than a 12x24x1, which is the more common variety you have likely been considering. If you imagine a speck of paint landing on the filter and sealing a portion of it against airflow, the more surface area you have on the filter, the less proportional airflow you’ve now lost as a result of that speck of paint. Now, in real life, those specks are nearly microscopic, but the concept holds true nonetheless; a thicker, pleated filter will maintain lower static pressure for longer than an equivalent non-pleated filter.

       Reply

       • Stuart

         Oct 17, 2022

         Yes, that is all true.

         It seems that 16x20x4 is the smallest thicker pleated filter readily available.

         But what would be better, 16x20x4, or 16x20x1 low efficiency filter + a 1″ pleated filter? Or maybe even pre-filter + pleated filter?

         Everything is cross-dependent, but it seemed like a good start to solicit help in making sense of blower fan and relevant airflow basics.

         Reply

6. MatthewJ

   Oct 17, 2022

   FWIW (very little), five years ago I bought a box of foam core sheets from the Dollar Tree and hot-glued a bespoke enclosure around furnace filters and a box fan that vents directly out a window. I only run acrylic paints through my airbrush, and I’m quite happy with my ~$30 investment. I found that not buying lacquers or enamels greatly reduces the urge to spray them ‘just this once’ 😀

   Reply

   • Stuart

     Oct 17, 2022

     I like to overdo things. =)

     In all seriousness, I’m approaching this project as a potential skill-builder. Today I want a customized-size airbrush paint booth for acrylic. Maybe at some point in the future I might want a ductless fume hood for mixing and curing epoxy. I used to work in a lab, and didn’t have complete understanding of how it worked. Understanding specs here can help in case I’m ever in a lab again and need to shop hoods for whatever reason.

     Reply

7. MM

   Oct 17, 2022

   I have built a DIY spray booth before, though mine was quite a bit larger than what you are asking about. Mine was roughly 24×36″ square, I built the box out of plywood and set it up to take residential AC filters to catch the paint overspray. I had one cheapo filter in the front to catch most of the spray and then a pleated one behind it. My discharge duct was quite short, maybe only 5 feet total length so I didn’t have to deal with much backpressure. My thoughts:

   1) You need more airflow than you might think for this. I have used many of those Dayton blowers from Grainger for various projects but I didn’t think those small ones would have sufficient airflow, and as you found out the large blowers quickly get expensive. My solution was to buy a Grizzly G1028 dust collector and just use the blower off of it, If I recall correctly that was rated for around 1300 cfm and I considered its performance marginal.
   2) You want a radial blower–centrifugal or “squirrel cage” blower. Axial fans won’t handle the pressure drop across the filter and through long discharge hoses very well unless you are buying very very costly turbines.
   3) This probably goes without saying given your expertise, but make sure you ground everything well. You’re dealing with flammable solvents, fans and moving air can generate static, make sure everything is well grounded and whatever duct you’re using to discharge the vapors is conductive.

   An alternative you might consider instead of discharging the air outdoors via a duct is to trap it with a carbon filter. Depending on how much work you’re doing, something as simple as taping a cheapo AC filter to a carbon HVAC filter and then taping that to a 24″ box fan might be all you need. Cheapo filter catches most of the pain particles, carbon filter traps the vapor.

   Reply

   • Stuart

     Oct 17, 2022

     Thank you!

     I considered using a dust collector blower (Rockler has a couple with convenient mounting), but they are larger and noisier than I was hoping for, not to mention pricier.

     Grounding seems important, but I intend to use non-flammable paints exclusively.

     I have been considered a discharge filter box with carbon filter trap, but I haven’t had luck in finding good recommendations for carbon filter materials.

     Industrial suppliers sell it by the roll.

     BUT, I’m also hesitant; I’ve read is that carbon filters don’t do a lot to absorb vapors, which you really need activated carbon for – and lots of it.

     I figured that’s something I can look into later, as it shouldn’t materially change the blower selection or main overspray box design.

     Reply

     • MM

       Oct 17, 2022

       I have seen two main kinds of carbon filters out there. I don’t know what the technical terminology is for them, hopefully an HVAC pro can step in, but:
       The first kind resembles a normal residential HVAC filter. They are often pleated, but the point is that they are thin. These may work for nuisance odors but they are not what I am suggesting.
       The kind I am recommending, and I have used before in a lab setting for organic solvents, is much thicker, the ones I used were at least 2″ thick. These were a plastic honeycomb which was filled with granular activated charcoal. If you shook it you could hear and see the grains of charcoal moving around. That kind, whatever it is properly called, should work.

       Reply

       • Stuart

         Oct 17, 2022

         The latter is activated carbon, and most applications I’ve seen involve pounds of it.

         Reply

         • MM

           Oct 17, 2022

           They are both activated carbon, the difference is how much is there. It seems that many of the residential “carbon filters” just have a tiny layer whereas the latter example was just like you described–a few pounds of the carbon material. Anyway, I can confirm from personal experience that such a filter works for organic solvents so I’d imagine it would work fine for paint vapor so long as you have some kind of mechanical filter in front of it to catch the paint droplets so they don’t clog up the carbon.

         • Stuart

           Oct 17, 2022

           Sorry – I meant granulated active carbon.

8. Farid

   Oct 17, 2022

   The 100 fpm recommendation for paint booths comes from OSHA standard, and is considered to be the minimum capture velocity. When I used to consult on industrial ventilation (long time ago!), we used to take airspeed measurement in a grid across the opening of the booth and the average must be 100fpm or more. Typically, the center has the slowest velocity and the near the edges has the most. The standard also assumes that you are painting inside the booth, not spraying from outside into the booth. We used smoke tubes and smoke “bombs” to show clients and evaluate the flow around the booth. Shallow booth had terrible airflow consistency vs. deeper booths.

   Ashrae used to have some recommendations on capture velocity. It depends on the type of spraying you are doing. The higher the paint velocity, the higher the capture velocity required. The smaller the atomization and volatility of the of the paint carrier, the higher the velocity required as well (if my paint was MEK based , I’d want a lot more airflow than if it was water based).

   For airbrush painting, you probably don’t need a lot of airspeed, but you should make sure the air is flowing where you need it. Most of the small paint hoods on the market have a tapered opening, which is the stupidest design (we have one at my work as well). The object to be painted is typically sitting on the bottom, but all the air short circuits near the top of the opening straight into the exhaust pipe. If you are getting one of those, then I recommend is adding a sheet of polycarb. to block the top portion (similar to lab hood). This will cut on the amount of required air significantly. The smaller the front opening, the more effective the capture.

   Speaking of lab hoods, there are usually tons on the surplus market and a lot them have and adjustable door sash and have better airflow distributions than paint booths. You do have to add filter media to them though.

   The blower sizing is the last stage in the design. You size your blower based on the airspeed you want to maintain, allowing for losses in the filter, duct, elbows, and reducers. The higher the duct air velocity , the higher the losses. Unlike dust collectors, since the filters are supposed to capture most of the paint particles before going into the duct work, you don’t have to worry about settling and minimum duct velocity so much, so in this case, try to maintain as large duct-work as possible, matching the blower intake. Industrial ventilation systems with complicated duct work can have quite a bit of static pressure losses, but in your case, the most loss will come from the filter, so look at the the required pressure across the filter and add a buffer for filter loading , I would shoot for 200FPM.

   Since you mentioned grinding and other operations, capturing grinding dust is trickier because grinders throw particles ate very high speeds and typically require very high capture velocity at the source (>600 FPM). If you can get your hands inside the booth and have a window to block a portion of the opening, then you can probably and safely multitask in the hood. Just don’t do anything that generates sparks!

   Regarding Power factor, inductive loads with lower power factor actually draw more current than ones with higher power factor. A power factor of 1 is purely resistive load.

   Reply

   • Stuart

     Oct 17, 2022

     Thank you – that certainly makes a lot of sense, and I appreciate the direction in overspray box design!

     I meant more rotary tool sanding and grinding – things that produce very small amounts of materials. I have a small vacuum hood and scoop for this, but it’s a hassle to setup for small tasks.

     As I don’t intend to airbrush heavily, having a dual-purpose box increases the benchtop or storage footprint justification.

     Reply

9. Koko The Talking Ape

   Oct 17, 2022

   Air filter design is surprisingly complex, maybe because the finished products look so simple.

   I think you said or implied this, Stuart, but I’ll lay it out, mostly to clarify it in my own head but also in case it helps somebody: air flow, like water flow, is a lot like DC electrical current. Both require two numbers to describe them: cubic feet per minute or CFM (analogous to amperage) and pressure (analogous to voltage). You need both numbers.

   So in choosing a fan, the question is not just how many CFM it can produce, but how much pressure.

   A filter will reduce both pressure and CFM in the flow, so your fan will have to overcome that.

   So if it were me, in choosing a fan I would overkill with the pressure, not the air volume. The reason is that you won’t be creating much overspray or solvent vapor with an airbrush. You just need to create enough air movement to move those tiny droplets, vapor and paint dust. But the filter can really hurt air pressure.

   According to your chart, squirrel cage (centrifugal) fans create higher pressures more easily. I notice that air purifiers tend to use squirrel cages, maybe for that reason (also maybe because of their shape or configuration). (I have two air purifiers in my place, and I’ve owned several more. All used squirrel cage fans. They were all pretty large, almost two feet in diameter, probably to allow them to turn more slowly and thus more quietly.)

   If you are worried about the CFMs from a squirrel cage fan, you can always use two of them in parallel (like two batteries in parallel, to increase available amperage.)

   Hm. Maybe you could salvage a fan and motor from an old air purifier. If they can produce decent airflow with a HEPA filter, I’m sure they can handle a furnace filter, even a good one.

   Re explosion-proofing, you won’t be creating much flammable vapor, if any, and I’m sure it will almost immediately be diluted well past its flammable concentration. So I wouldn’t worry about that.

   But just thinking about it, I suppose a brushless motor would be good, because they don’t create those little blue sparks you see in brushed electric drills and such. Or you could run the fan with a pulley, and place the motor out of the air stream.

   Just some thoughts! Don’t mind me.

   Reply

   • Stuart

     Oct 17, 2022

     Water flow would be the more direct analogy, but electrical current flow can work too.

     A filter can potentially have the same effect as a light bulb on an electrical circuit, where its inherent resistance will cause a voltage drop. As a light bulb’s resistance can increase with temperature, the resistance (static pressure drop) of a filter can increase as it’s loaded with captured particulates.

     I have seen the double squirrel-cage blowers, but that seems more complex when a single larger blower might work the same.

     Reply

     • Koko The Talking Ape

       Oct 18, 2022

       Two squirrel cages would be more complex, but only in that there are two of them. The wiring would be very simple, not? ”

       I suggest it because sometimes two small blowers might be more compact or lighter, or easier to mount, than one big one with the same capability. That one big one will have a big impeller, meaning it’s slower to spin up, needs heavier bearings, maybe more likely to be unbalanced, etc.

       Reply

10. BK

    Oct 17, 2022

    Oven hood.
    Ages ago, ripped out my kitchen down to the studs. Saved the Oven hood.
    Built a cardboard box for that old oven hood ( it had pretty thick multi-level filters) , worked great for years. Never got around to venting it outside, but the hoods are designed to do so, if you wish. And really not expensive.
    Remember these are designed to be used over an open flame, hot oils, vapors, and gas stoves (with their filters).

    Reply

    • MM

      Oct 17, 2022

      Most oven hoods have terrible CFM for this purpose, but if you happen to have a good one that wouldn’t be a bad idea at all!

      Reply

11. MtnRanch

    Oct 17, 2022

    Simplel solution.

    Since you are only talking about a low volume airbrush, put the fan outdoors and attach it to a “wye” of appropriate size for the fan. Run a duct from the other inlet to the “wye” back to your spray box inside. The smaller the angle on the “wye”, the better.

    The vacuum created by the fan pushing air through the “wye” will draw air from the spray box. Doing it this way eliminates the filter and the noise plus you don’t need a filter and the spray isn’t draw through the fan.

    The only disadvantage I can see is that it will draw conditioned air from the indoors and send it outside – really only important in summer or winter. Airbrushing usually doesn’t take much time or air volume so it may not be that significant.

    Reply

    • MtnRanch

      Oct 17, 2022

      PS. There are commercial water pumps based on this principle that just use water flow to suck water out. Seems counterintuitive but they work. Also, you may have to experiment with the length of pipe necessary on the output side of the “wye” to get optimum suction. This is just a good excuse to buy a hand-held anemometer.

      Reply

    • Stuart

      Oct 17, 2022

      What you’re describing is a Venturi effect vacuum/pump. This is widely used for a lot of applications, such as using compressed air to create a vacuum, or water pressure for a backup sump pump.

      Ejecting paint spray to the outside environment is not ideal – an overflow box is much more effective at capturing it.

      Even when I spray anything outdoors, I use a pop-out spray shelter to contain the overspray.

      Reply

      • MM

        Oct 17, 2022

        I think he’s just suggesting this as a means of moving air instead of a blower. You could still use a filter to catch the paint residue in conjunction with it.

        Reply

        • Stuart

          Oct 17, 2022

          “Doing it this way eliminates the filter and the noise plus you don’t need a filter and the spray isn’t draw through the fan.”

          He’s suggesting a way to use a blower fan to exhaust air without the atomized paint passing directly through the blower.

          Looking online there *are* venturi spray booths that contain or recycle paint droplets, but they seem to have huge airflow requirements.

          Reply

12. Nathan

    Oct 17, 2022

    one big issue with your idea is the fully open front end it makes the math modeling very complicated and inaccurate. So it’s a test and try work. Those OSHA requirements are the installation tested not just the fan moves 100 cfm – or it was the last time I used it. I was dealing with a car paint booth however and with doors closed – while still open with air filter media it’s not a flared out opening.

    Also for your filter needs there is a reason to use that plastic media for your paint – make your box such that oyu can use that thicker media and exchange it – but also if you want to do dust collection consider that you could also drop a different filter in there. 2 goals – 2 different filters.

    also are you planning to use a mask/respirator for you and are you worried about the fumes for others in your workshop. If you are not worried so much about fumes in your workshop worry less on the charcoal filters. vent it outside and let it go.

    Not my normal thing either so good luck and keep us posted it’s an interesting idea.

    Reply

    • Stuart

      Oct 17, 2022

      I figure that a box can be modified and rebuilt, but motor selection requires knowledge and insights that would be very expensive to learn via trial and error.

      Trial and error still needs a starting point. Many “DIY paint booths” involve slapping filter material on top of fans, but I was hoping for a better understanding, at the least for more strategic trial and error.

      I’m mostly worried about immediate overspray and lingering particulates.

      I’ve sprayed with a respirator before, and was shocked at how much paint was captured by the pre-filter.

      I’m not worried about fumes – that’s why I prefer acrylics – I’m mainly worried about not breathing in paint, and not letting paint float around and land on places it shouldn’t be.

      I have a ceiling-mounted air cleaner in the garage, (as close to a wall as I could place it) and can open doors for quick ambient air exchange.

      I use vacuums or dust extractors to pick up sawdust as it’s created, and the air cleaner if I feel there are too many suspended fine particulates but cannot open the garage doors for quick air exchange.

      Even then, stray sawdust is easily cleaned. Landed paint particles are not.

      The way I see it, for my intent to use acrylics, ducting airbrush exhaust outside is focused on my not having to think about where to direct it inside.

      Reply

13. Ct451

    Oct 17, 2022

    Or space out the flow by using a bunch of these one next to each other:
    https://www.digikey.com/en/products/detail/sunon-fans/SP101A-1123HST-GN/1021237
    There is no need to squeeze all the effort in a small area and dilute it as you expand. You save on mounting hassles of a big fan as well. All you need is a piece of plywood and a hole-saw. It really cuts down on the noise too.

    Reply

    • Stuart

      Oct 17, 2022

      Computer fans are great for cooling purposes and certain air movement applications, but do not handle restrictions very well.

      6x good 120mm or 140mm fans, plus a power supply, and there’s not much saved vs. the cost of a blower fan.

      That’s something I might try for fun comparison, but I’m not certain it would work well for this.

      Reply

      • Ct451

        Oct 17, 2022

        These are 110v. Silent blower fans are very expensive so people use these for venting recording booths etc.

        Reply

14. James+C

    Oct 17, 2022

    I don’t have any advice on airbrushing but this may be relevant. I bought a cheap laser engraver and built an enclosure for it. I rigged up some exhaust fans and ducting for the box to blow the fumes out a window. It works ok but needs some revisions.

    I don’t have much free time these days, and with my little laser project I’m probably at 20% of my time using it and 80% configuring, tinkering, etc. I would have been much better off spending 2 or 3x to get something that works right out of the box so I could spend my precious time actually using the dang thing.

    Reply

15. Kurt

    Oct 17, 2022

    I built a spray booth based on that “Build your own spray booth” article.

    https://www.facebook.com/kurt.greiner.7/posts/pfbid02JQ8iGVUnX3X6xXwi4KJyCb35SEikqSXfweB1jKFzdYjVSYYdVL91XipFEHvC232ul

    I ended up buying the recommended Dayton 6FHX9 and it has worked very well, quiet and more than adequate airflow

    Reply

    • Stuart

      Oct 17, 2022

      Thanks, I’ll take a look!

      I’m still eager in understanding why that model when the 1TDR3 moves the same air but with lower power consumption due to its motor type.

      The 1TDR3 cost less than 6FHX9, and everything I’ve been reading says it’s a better type of motor.

      The 1TDR7 is larger but moves a lot more air, also for less money.

      Reply

16. Andy H

    Oct 17, 2022

    If I were going DIY on a budget, I would use a couple of USCG-approved bilge blowers, which you can buy from reputable brands like Attwood for $25 each. These are designed to vent FLAMMABLE gases (like gasoline vapor) out of your bilge and engine compartment before you start your engine.

    Even if you’re spraying non-flammable acrylics, you might at some point decide to mix in a retarder or smoothing agent that is volatile enough to burn.

    Also, I prefer having a spray booth with the filter and intake on the bottom surface of the booth. On top of the filter, I place a sheet of thin, open-cell foam. Positioned this way, the filter catches more of the overspray directly, and I can also test my paint & air mix by shooting right at the foam sheet.

    I’ve owned multiple airbrush booths over the years, and my favorite is the MicroLux booth from MicroMark that I bought over 20 years ago, but it’s wicked expensive these days. If I needed another booth, I would copy the MicroLux’s design and build my own with HDPE sheets and bilge blowers.

    Reply

    • Shawn+Y

      Oct 19, 2022

      This one, right? https://www.micromark.com/15-Inch-x-30-Inch-Large-Spray-Paint-Booth

      That is pricey but the design and specs seem to be a good source for diy reference.

      Reply

      • Andy H

        Oct 19, 2022

        Yup, that’s the one. I think I paid half the price it’s going for now.

        Mine has a translucent top surface with a flourescent bulb. I keep telling myself that I’ll replace the bulb with daylight-temp LEDs… but too many other projects on my list!

        Reply

17. Ryan

    Oct 17, 2022

    100 feet per minute is the target velocity at the part. When I measure our industrial spray booths (for plastic automotive interior parts) at around 4″ from the exhaust filter we get around 250fpm. This won’t translate 100% from a production booth down to a small scale batch booth, but we are spraying 250 – 400 cc/min of solventbase paint with robots and all of the performance and safety specs that people are mentioning matter. With an air brush, you barely have any material in the cup. A basic 1″ pleated exhaust filter should be fine for the low volume of material being sprayed.

    One bit of advice is that you should be aiming for adequate flow velocity to catch overspray, but it is not necessarily a “more=better” property. Too much velocity will cause your paint to shoot past what you are painting and go into the filter instead of the part.

    I would advise starting simple and not overthinking things too much. A blower style fan would be needed if exhausting outdoors through a small duct. Otherwise, the filter and box fan method is not a bad route all things considered. The Paint Engineer that preceded me used that for airbrushing fishing lures as a side business with great success. He had the fan set up to blow out a window directly outdoors. This may or may not be feasible in your layout, but box fans are cheap and, if nothing else, it could serve as a good prototype to figure out what things are actually important to you to help alleviate some of the analysis paralysis.

    Reply

    • Stuart

      Oct 18, 2022

      Thank you for those insights, I appreciate it!

      At one time I had a double fan window unit; something like that would be great to get started with here, but I don’t have convenient window access.

      I have some ideas on how to experiment with simple designs, and with everyone’s help I feel more confident about the trial and error directions. The variables seem less daunting now.

      Reply

18. Nathan

    Oct 18, 2022

    were those fan motors even available when the device was designed? I wonder if maybe the reason they use a less efficient motor is more about availability and use at the time of creation. I see nothing wrong with using either of those “7” series motors. Absolutely would use a split capacitor motor today if the cost was near the same.

    Reply

    • Stuart

      Oct 18, 2022

      Maybe? I’ve been looking into the model numbers and have found random forum posts (usually in regard to airbrush spray booths) mentioning those blowers, going back years.

      It looks like the recommended motor is/was made in the USA, and the PCS fans are imported.

      Reply