Vent/filter setup for spray booth

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Forum topic by theniteowl posted 03-18-2015 04:36 PM 1364 views 0 times favorited 6 replies Add to Favorites Watch
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6 posts in 3260 days

03-18-2015 04:36 PM

Topic tags/keywords: spray booth ventilation filter question

Hi All,
I am looking to put together a temporary spray booth in the basement to spray some kitchen cabinets.
In all the searching I have done everyone seems to use a fan blowing out of the booth often through a window.
I was thinking of going the other direction and using a ventilator fan to pull air through a filter from inside the house.
I picked up an 8” ventilator fan from Harbor Freight that is rated at 1590 CFM on high and 1380 CFM on low.
My thought is to build a box to hold a filter that is exposed to the inside of the house and to mount the fan inside the box pulling air through the filter and blowing into the spray booth. The idea is to pull fresh air into the booth with an outside vent on the other side of the booth for air to move out. The filter is to prevent dust from entering the booth from the house and perhaps I would need another filter to capture airborne paint rather than let it just blow outside and land wherever it happens to.

Any thoughts on this method rather than on a fan blowing out from the booth? I do not want to pull paint through the fan of course and this seemed like a good way to avoid that. The higher volume of air might be an issue inside the booth but I can always split the air intake and manually adjust the flow.

I will be using an HVLP sprayer and want to keep the air clear. I plan on using waterborne paint so the fumes will not be bad, mainly I want to keep the air clear of dust and paint.


6 replies so far

View Mosquito's profile


9541 posts in 2495 days

#1 posted 03-18-2015 04:48 PM

So, just so I’m clear here… you’re talking about using positive air pressure, by blowing air into the booth?

I’d be hesitant to do that myself, as that positive pressure will end up making any less than air tight areas release into the room what you’re trying to exhaust.

This comes from a member on a computer case modding forum that I’m an admin on:

This was the later revision as well.

I know it doesn’t necessarily fit your “not pulling exhaust through the fans”, though. Just food for thought.

-- Mos - Twin Cities, MN - -

View levan's profile


472 posts in 3182 days

#2 posted 03-18-2015 05:02 PM

Sorry not a good idea. The entire house or booth if sealed would have to be pressurized before it finds its way out.
Exhausting to the outside with filter ahead of fan is the way to go. I’m not sure that 1590 cfm is enough air movement. You need to calculate the size of the booth to determine this. In commercial settings an air make up unit is used to blow in air and heat it if necessary, but they also have a bank of filters and exhaust fan to pull the air out of booth. The exhaust needs to be sized with more cfm than the intake, otherwise it will pressurize the building, and fumes will go everywhere.
best wishes

-- "If you think you can do a thing or think you can't do a thing, you're right". Henry Ford

View theniteowl's profile


6 posts in 3260 days

#3 posted 03-18-2015 05:34 PM

I was afraid something like that would come up. I had considered the positive air pressure but thought I could make up for it using a larger outside vent. Certainly trying to maintain an air tight seal is beyond reasonable for a temporary booth setup.
Do commercial booths tend to locate the air intake higher or lower than exhaust? I am wondering what would make for the best air movement through the booth. I imagine in most cases the particles will be heavier than air so an exhaust near the floor and an air intake higher up would allow the best movement but I have no experience with this and there have to be many details I have not considered.

Thanks fo the replies.

View levan's profile


472 posts in 3182 days

#4 posted 03-18-2015 06:07 PM

In our commercial booth the entire back of the booth is covered with filters and the air intake is all along the top just outside of the booth. We have always found that the bottom filters do plug up faster, so your probably right about the weight of finish wanting to go down. Since your using water based, no worry about explosion.

Cleaning booth area really well ,with exhaust running normally is sufficient to get rid of dust particles. We do use an air hose to blow off the walls etc. Some people even mist the floor with water to hold the dust down.

I think the biggest thing is the volume of air moving so dust and over spray, don’t just hang in the air looking for some finish to land in. And enough filter area so you don’t restrict the air flow.

here is and interesting idea.

best wishes

-- "If you think you can do a thing or think you can't do a thing, you're right". Henry Ford

View OSU55's profile


1972 posts in 2192 days

#5 posted 03-18-2015 08:29 PM

Since you plan to use waterborne paint, pulling the paint into a filter, through a blower, and exhausting outside will work just fine. When cool outside I just discharge back into the shop (with waterborne, and I always wear a respirator). I open the garage door and a door in the back wall and let fresh air wash all the fumes out periodically – a bit of a fog does build up in the room after about an hour of spraying (non-flammable, waterborne remember?). When warm out I exhaust fumes outside and pull in outside air.

The blower you have will provide plenty of air movement. My blower moves ~1000 cfm through a booth 10’ wide by 10’ tall. The blower is in a box that sits on the floor, with 20” x 20” filters on each side. I move each piece to be sprayed into the area in front of the blower, and then hang each piece upstream. Larger pieces get positioned on the floor or whatever stand in front of the blower. There is enough air movement to prevent overspray getting on the pieces “in waiting”. Part of that is being smart about where the overspray will go. I do not filter the air coming into the booth – the entire 10’x10’ end of the booth is open – the booth has 3 walls. I turn the blower on for 30-60 minutes before I start spraying which cleans the air well – I don’t get many dust nibs.

View theniteowl's profile


6 posts in 3260 days

#6 posted 03-23-2015 05:32 PM

I will modify my plans for the booth to keep it narrow and facilitate air flow.
The spray booth will be in a dusty basement so I will need to have a filter for the incoming air to keep dust out but I can use extra filters to decrease the air flow restriction and try and maintain a relatively static air pressure in the booth.

Thanks for the advice everyone.

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