How much CFM is needed for a home made spray booth

Phule · Post by **Phule** » Sun Mar 30, 2008 9:44 pm

Well, the topic says it all.

I was about to start flooring in some of the attic with 1/2" 4x4s, when my wife decided she wanted to redo the room above the garage. Sooo.. out comes the 4x4s and in comes the contractor with his flooring and a new room for the family.

So now I have 6 1/2" 4x4s and need/desire of a spray booth. I went to Lowe's and noticed that 100cfm were under $80, is that enough, or do I need to look at a bigger unit.

Any help would be appreciated.

Lt. Z0mBe · Post by **Lt. Z0mBe** » Fri Apr 11, 2008 9:59 pm

Mine's 35cfm and does fine. Robb (kylwell) has one that's 1cubicgigafoot or something and it works. I think you'll be fine.

I hope this helps.

Kenny

Phule · Post by **Phule** » Sat Apr 12, 2008 6:10 am

Thanks LT.

It does answer my question. Now to just build the rest of the spray booth.

Kylwell · Post by **Kylwell** » Sat Apr 12, 2008 11:15 am

Mine is 80 cfm per cubic foot of booth space. Lots of air but I can spray lacquers without smelling the house up.

Other things to consider (when designing ones own) is a large enough draw area for the fan. If you're running a 100cfm fan through a 4" hole in the back of the booth you won't be getting the full draw.

Oh, and those el cheapo furnace filters make a great first stage filter.

kenlilly106 · Post by **kenlilly106** » Sat Apr 12, 2008 11:49 am

A couple of other things to consider:

1 - Make the duct run as short and as straight as possible, a long or twisty duct will not vent properly.

2 - Make sure you have a source of fresh air to replace the exhausted air, an open window works fine, otherwise the booth will not vent properly.

Ken

Kylwell · Post by **Kylwell** » Sat Apr 12, 2008 12:13 pm

kenlilly106 wrote:2 - Make sure you have a source of fresh air to replace the exhausted air, an open window works fine, otherwise the booth will not vent properly.

Ken

That depends on the size of house/apartment and room.

I've got a 400sf room in a 1500 sf house, never had the need to open a window (which if you do needs to be away from the exhaust area, otherwise you just drag all those fumes back in). If you have a forced air heating system you won't need to as the system has a cool air intake, provided the room you are in has a heating vent.

kenlilly106 · Post by **kenlilly106** » Sat Apr 12, 2008 1:23 pm

As you said, it depends.

I've read on various boards where people have a new booth with a powerful fan and are complaining it won't work after a while, they think that all they have to do is turn on the fan and their problems are solved, they don't realize that they need make up air to replace what goes out.

If you have a really tightly sealed house/room/modeling area/man cave, the issue is that once the fan is on for a while, it will reach a point where it's pulled a partial vacuum on the area and can't exhaust any more.

There's a very big danger if you paint in a basement with a gas appliance, if the basement is sealed tight, the fan can try to pull fresh air down the chimney, which in turn pulls carbon monoxide with it.

Ken

eeun · Post by **eeun** » Sat Apr 12, 2008 1:25 pm

Since you're starting from scratch, something you might want to consider is adding in a rotary dimmer switch for the fan.
I found I didn't always need the fan going full-tilt, and the dimmer lets me turn it down to a gentle - and quieter - draw for when I'm letting parts dry in the booth, or even if I'm airbrushing with very low pressure.

Lt. Z0mBe · Post by **Lt. Z0mBe** » Tue Apr 29, 2008 10:25 pm

Also, you may consider adding a light and a hinged opening.

This will help keep the dust out and make your paint booth double as a drying area. That's how I did mine.

I hope this helps.

Kenny

Phule · Post by **Phule** » Wed Apr 30, 2008 12:27 am

that is exactly what I want Lt.

what are your dimensions for it?

scottgirvan · Post by **scottgirvan** » Thu May 01, 2008 3:23 pm

I made mine with an old microwave stand (ala Walmart). I just added a box on top with old plywood, put a $30 bathroom fan onthe back, cut a hole on top and added a flea market aquarium light and a hindged plexiglass door. It works great. Compressor fits under it too.

I have no pictures of it. It's in storage until we finish the reno. You can do it. Just get some wood and a saw and a hammer - and safety goggles.