Ventilation For A DIY Paint Booth

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PostPosted: Wed Apr 21, 2021 5:34 pm
Hi Guys,

I have built a 10'x8' tin shed to use as a booth for shooting small parts. The flooring consists of patio slabs grouted and painted with white cement paint. I have sealed every gap I can see light thru from floor to celling with spray foam and silicon and installed 6 eight foot LED lights--it's brighter than daylight!! Thought I had the ventilation planned but am second guessing myself.

I have two 20" three speed box fans. One for air intake and the other for exhaust. Both will have a furnace filters on them. To my way of thinking, I would want to exhaust the fumes/overspray down low (kind of like a down draft style). Than would mean the incoming air would come from a higher level roughly opposite the exhaust. Am I correct thinking this way? Any advice is really appreciated!!



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PostPosted: Wed Apr 21, 2021 8:18 pm
O.K. thinking on the fly....maybe make a 12"x12" hole for the exhaust fan and an equal or smaller one for intake (no fan--just natural air coming in (filtered of course.). Perhaps 2 fans (1 sucking and one blowing will cause too much air movement in such a small space and potentially stirring up any dust). Still having the intake air up high and the exhaust going out low--creating a draft. Thoughts??



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PostPosted: Wed Apr 21, 2021 10:19 pm
General Ramblings of an old Fart drinking beer:

Not to be a Dick but It wont work you'll have a wind tunnel.
ASK me how I know?
(Because it was my first attempt!)
(I made several other attempts before giving up and buying a Used booth!)

Proper Paint booth air flow design is hard to achieve without some thought about how to get the whole booth to move air freely through the whole room at the same time without a Breeze or wind in it. Its easier said than done! ALL the air in the booth needs to move NOT just one section but the whole Booth ALL The AIR. You want it all to slowly move to the filters you want a total air exchange not a wind tunnel.

In short You need a Bank of filters and a Plenum box.
A plenum box allows a Bank of filters to work as one filter.
Without enough surface area you force all the air to go through one or two filters and you will have a Wind or breeze that will disrupt your Paint guns spray pattern and it don't take much to disrupt it.

I would use at least 8 20 x 20 air condition filters and a Box at least as big if not 1/3 larger than the filter bank, and at least as deep as the filters are wide.
Mount fan on other side or at the top to draw the air through ALL the filters so the air blows out side.
The Air Intake side needs to be the same size and amount of Air filters used for the exhaust side In this example 8 no need for any Plenum.

Look at real Paint booths you'll see what I am talking about.
Also you may be further ahead going with a Positive flow rather than a Draw through.
A positive flow booth while more dangerous can provide for cleaner paint jobs as you don't have a Vacuum sucking in crap from every leak in the Booth.
It Is more dangerous Though because your effectively pressurizing a box with atomized flammable chemicals so one good spark and Boom!
Not to mention you have a Fan fanning any fire.
Good reasons to frown on the Positive pressure booth idea.
The fire department don't like them at all!
No matter what you do want to make sure your fans are of a BRUSH LESS design that way you don't have any sparks from them any way!


My Booth looks like this note the Large Plenum box below the exhaust fan.
Image


Another thought for you
A paint booth while it does provide a Clean room to work in IF it is kept clean!
But Clean Paint jobs are not the Primary purpose of a Spray Booth.
The Primary function is to collect over spray and Trap it in your filters so over spray doesn't get all over anything out side of the spray area I.E. other cars buildings etc.
Beleave it or not its a true fact.
Dennis B.
A&P Mechanic, FCC General radio Telephone Operator
Line Maintenance A&P Mechanic and MOC Tech specialist.

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