"Paint Booth w. Act. Charcoal Filter" Topic

I discovered plans, on the Internet, to build an indoor spray paint booth, with an external, activated charcoal filter, for indoor use -- no venting through an exterior window! The activated charcoal will absorb the VOC's (stinky, flammable, chemical fumes and off-gases from solvents). His system used a 5-gallon bucket, with the charcoal filter, external to the spray booth, which had a particulate filter in it, to capture the over-spray paint particles, which would ruin the charcoal filter very quickly. That was too big, too complex, too much work.

I recently searched YouTube for videos on building a spray paint booth with a charcoal filter. Most did not incorporate the charcoal filter within the single booth housing with all of the filters built into the whole.

I took ideas from several videos, mixing and matching the bits and bobs that I liked, to come up with one that suits me.

I built mine out of foamboard: easy to cut, strong enough for the light duties a spray booth hood will experience. I bought the smallest furnace filter I could locate at my local DIY store: 10" x 20" x 1"; note that blue fiberglass filters would not capture very many paint particles, so I went with a more robust type of filter sure to capture the paint particulates. Then I had to decide whether to put the activated charcoal all across the back of that filter, or reduce it to a smaller area just covering the 4" duct fan I bought to pull the fumes and gases out of the box?

The box's dimensions are 18" x 20" x 11" deep. All seams have been glued and air sealed using Low Temperature Hot Glue. White Duct Tape would be faster, and easier, to use, but the seams would not be as rigid.

I decided to cover the entire rear surface of the 20" x 10" furnace filter with the activated charcoal filter, to distribute the chemical fumes across a much larger filter area. This should make the charcoal filter last much longer (less work for me to change filters!).

I learned that if I build a reduction box (like a capital Y, turned on its side), which channels the air coming out of the furnace filter evenly down to a 4" square box, with the round fan in the center, the air pressure across the filters should be even, allowing the paint to be drawn all across the entire surfaces of the filter set, rather than just in a circle the size of the duct fan.

I built the booth box around the furnace filter size. The filter is only 10" tall, so the air will be drawn downwards, to the filter across the bottom of the box. This is not as efficient as I would like, but paint particles will fall because of gravity, so the air draw will help them drop to the filter.

The inline duct fan, 140 CFM draw, cost me $20 USD off of e-Bay; the duct fan is NOT explosion proof, so that is another reason to use activated charcoal filter, to capture the VOC's before they pass through the fan's motor area which likely has brushes sparking. The four sheets of foam core cost me $16 USD, at Wal-Mart; the furnace filter was about $8 USD, and the activated charcoal filter sheet was also $8. USD I used 6-8 Hot Glue sticks to build the boxes with. The total materials cost is roughly $52. USD Recycling a cardboard box would have saved around $16 USD by not needing to buy the foam core boards ($36 total, instead of $52 USD).

I finished the initial spray booth box, in a couple of hours. I have the reduction box to build yet. I also need to install some tabs to gently hold the furnace filter in place, and the activated charcoal filter will be sandwiched between the boxes filter stop guides, and the furnace filter. I hope to finish building the air reduction box in the next two nights. I have some spray painting to do, and the outside temperatures are barely above freezing. The booth will allow me to paint whenever I want, in my basement crafting/miniature painting room, regardless of the weather conditions outside. With the activated charcoal filter capturing the VOC fumes, it will be safe for my wife and I, as well as our dog!

I will post more pictures and updates, as the project progresses. As Red Green says, "Remember: if the women don't find you handsome, they ought to find you handy!" Cheers!

Really interesting project! I would like to see photos and see how it works out.

Grelber

I had planned on building something similar at my old house where I had a basement. Bought all the stuff with an explosion proof fan. Then I moved and there is no place to use it so it did not get built. Yet.

Good luck with your booth!

That is very interesting! Thanks for the info Sgt!!

I chose to make a 5" square to hold the 4" diameter duct fan. I realized that I could calculate the size of the reduction box using the right triangle equation: a-squared + b-squared = c-squared, where a and b are the right-angle sides, and c is the hypotenuse, That will help, quite a bit, in building the reduction box.

I cut out a 5"-square of foamcore, then I cut out a 4" hole in its center After that, I inserted the AC Inline Duct Fan, and I sealed it, on both sides, with Hot Glue. Here's another view of the sealed fan. I will mate up the reduction box to the fan, roughly in this position. That last photo shows the filter lock, on the left: I Hot Glued a bar of foamcore to hold that side of the filter, snugly in place (just below the wristwatch band); on the right side there is a smaller foamcore tab that I will push out, to get the furnace filter, and the activated charcoal filter sandwich held against the backstop of the hood (just above the red/black wires, in the photo). I hope to finish building the reduction box, tomorrow, so I can do some spray painting inside of it, on Sunday. Cheers!

It is done except for the electrical cord being attached to the motor. I need to find a cord I can use, along with a couple of small wire nuts, and a roll of electrical tape to wrap up the wire nuts. No switch, not needed; I will unplug it when I am done with it.

The whole unit is very crude. It took me back to my 7th Grade Shop Classes -- my skills are about at the same level now, as back then, 40+ years ago! The finished shape of the box took me back to my days training as an Electronic Technician, working on vintage vacuum tube TV sets, as training tools: the box looks very much like an old CRT TV, for shape!

I chose to apply cellophane tape to the gaps in the seams: I filled in the gaps using Hot Glue, then I peeled off the tape, after the Glue had hardened. I used the Geometry equation to come close to the right dimensions for my reduction box's sides, but nothing was cut precisely. After using the equations to get the two longer sides, I just held up foamcore pieces, and marked, and cut to (mostly…) fit.

It is sealed, it holds the two filters, sandwiched together. I hope to get the electrical cord done tomorrow, if I have time. I will take it for a test drive, in a few days, to see if the Activated Charcoal Filter does what it is supposed to do. If so, I will be very happy. Cheers!

I finished, and tested, the Paint Booth, tonight…  Results?  It is a partial success; it drastically reduces the odors/fumes, but spray paint goes right through both the furnace filter, and the activated charcoal filter. Here are some images for your viewing edification: front shot, of my d20 Globe, getting re-painted, after sanding; image of the exhaust fan, running, after spray painting dark blue into the Hood (notice the blue paint inside the fan housing, indicating that the liquid paint passed right through the paper and charcoal filters).

I could smell the VOC solvents, in the room, but they were drastically reduced from what I normally smell.  They were noticeable, but roughly 1/10 as strong, according to my laser-calibrated, mucus-lined, olfactory sensor array.  I will leave the fan running overnight, to filter out the off-gassing fumes as the d20 dries, over the next 12-20 hours, inside the Hood.

The blue paint inside the fan housing is undesirable, but it demonstrates the 140 CFM fan is, indeed, pulling the air through the filters and the Hood!  A 300+ CFM fan is not needed for this application.

I am disappointed that it is not as successful as I had hoped. It is still good, but it can be better. The advantage of the original design I found 20+ years ago, with the charcoal filters at the end of a 6+ foot long, clothes dryer vent hose, is that by the time the paint particles reach it, they would likely be complete dry! My charcoal filter needed to be duct-taped to the backside of the furnace air filter, as it was just barely big enough to cover the paper filter.

If a blue, fiberglass dust filter were employed, the charcoal filter would collect far more liquid paint, as much more of it would pass right through such an open filter. I will try a second layer of activated charcoal, to see if that will further reduce the VOC fumes, as well as the liquid paint particles exiting the fan housing.

The decreased VOC fumes reduces the risk of a fire in the fan motor. Experimentation is still King, Baby! Cheers!

Added a 2nd layer of activated charcoal filter, spray painted my d20 globe again… I could still smell fumes.

It still cuts the paint fumes by 80%-90%, but it is not 100%, like I had hoped. I still consider it to be mostly a success. I will continue to use it, indoors. Cheers!