Downdraft Paint Booth

[knightrw1110]

Hi all, I'm new to the forum and have been reading with interest various posts regarding paint booths. I've decided in the interests of keeping peace in the family to consider building one. Currently I'm in the early planning stages of a downdraft booth. I've got some questions that I hope you guys can help me out with. A) I'm thinking of using multiple computer fans in my "pit" area. Two in the front that will be blowing into the pit, and two in the rear that will be evacuating the pit. I think this will give me plenty of CFM, but will also create a venturi effect which should help pull the atomized paint and odors into the pit. B) I plan on using multiple filters. The first in the floor of the booth itself, the second and third stages in the pit. C) I would hook the fans up in series and run them to a rheostat switch so that I could vary the RPM and control my CFM that way. I've never built anything like this before, and so the vast majority of what I'm saying may not work. I'd like you guys to poke holes in this idea and let me know what I'm not thinking of, or why I shouldn't be doing any of it the way I'm thinking of. Thanks!

 

[Elm City Hobbies]

Hey there Knight,

I built my own, computer fans should work fine, don't know about 2 in the front and 2 in the back.

My own I used a 100cfm bathroom fan, extracted to the out doors. The work surface is just a piece of 1/4 peg board, over a furnace filter. The fan has been more than enough to pull paint vapors out of the booth, even with a spray can fogging everywhere. Fan itself draws enough air even through the furnace filter that a piece of paper towel will stick to the work surface, so plenty of suction to pull paint vapors out of the air.

 

[Drpepeprz]

I am looking onto building the same type of setup but I'm thinking about using a kitchen fan instead...

 

[knightrw1110]

Hey there Knight,

I built my own, computer fans should work fine, don't know about 2 in the front and 2 in the back.

My own I used a 100cfm bathroom fan, extracted to the out doors. The work surface is just a piece of 1/4 peg board, over a furnace filter. The fan has been more than enough to pull paint vapors out of the booth, even with a spray can fogging everywhere. Fan itself draws enough air even through the furnace filter that a piece of paper towel will stick to the work surface, so plenty of suction to pull paint vapors out of the air.

Hi and thanks for the reply. Yeah, I'm unsure of using all those fans. I don't want to create so much downdraft that I'm sucking in the leaves from the trees outside, and I know that a downdraft booth requires about half the CFM as a side-draft booth would. But those computer fans are small and generally develop way less in the way of airflow than a bathroom fan does. The nice thing is that they're small and they're darn quiet.

 

[knightrw1110]

I am looking onto building the same type of setup but I'm thinking about using a kitchen fan instead...

Hi,

Yeah, a kitchen fan would definitely work. Whats the size of one of them compared to a computer fan?

 

[Elm City Hobbies]

I would think you could find the cfm for the computer fans online somewhere. 4 fans, so cfm X 4.

There is more to it than that of course. If you want to get right into it, there is a way to calculate how much your fans will pull. I used to have a site bookmarked that had all the calculations, but can't seem to find it.

I know it had alot to do with the area that the fans are in (box under the work surface and filter) vs the amount of space above the work surface.

Mine is built around a 20"X16" furnace filter, and about 18 1/2" high and the 100cfm bathroom fan I have is just about perfect. Sucks the vapors out, but doesn't suck the air out of your lungs! LOL

 

[knightrw1110]

I would think you could find the cfm for the computer fans online somewhere. 4 fans, so cfm X 4.

There is more to it than that of course. If you want to get right into it, there is a way to calculate how much your fans will pull. I used to have a site bookmarked that had all the calculations, but can't seem to find it.

I know it had alot to do with the area that the fans are in (box under the work surface and filter) vs the amount of space above the work surface.

Mine is built around a 20"X16" furnace filter, and about 18 1/2" high and the 100cfm bathroom fan I have is just about perfect. Sucks the vapors out, but doesn't suck the air out of your lungs! LOL

Thanks for the responses. You've given me quite a bit to think about. Do you find that very much paint gets through the 20"X16" furnace filter and into your pit?

 

[Elm City Hobbies]

Not really. I just changed the filter I had after about 3-4 years of light use, and the area under the filter was pretty clean. The filter, not so much, so I guess it did what it was supposed to.

The new filter I bought seemed to be a little thicker, or more to it (sprung for a higher quality one), and doesn't seem to have effected how the fan evacuated the paint fumes any, so works for me.

I would show you pictures of it, but I think my photo provider is still in the process of moving their servers.

But having just looked, seems like those ones weren't part of the move, or they are working again.

http://public.fotki.com/ScottM/models/paint-booth/