External Exhaust Fan for spray finishing

[pierhogunn]

you guys have any suggestions for an external exhaust fan to evacuate a shop of spray fumes? this would be going through a cinder-block wall to the outside

Dan

[kenwarren]

Since dust is a problem with most finishes, consider either a filtered intake fan and simple (or filtered) exhaust port, or both intake and exhaust fans. With an intake fan, you're filtering air going in and slightly (very slightly, with most fans) pressurizing the room. With an exhaust fan, you're slightly depressurizing the room. The difference is that, when you pressurize the room, air blows out through all the cracks and crevices. When you depressurize the room, it comes in. Dust moves with the air, so an intake fan filters it out, then dust around cracks and crevices gets blown out of the room. With an exhaust fan, dust gets sucked in through those same cracks and crevices.

This is a trick that is sometimes used in photographic darkrooms, where dust is an even larger problem.

[maxparot]

Sprat fumes are difficult you need a good deal of flow if what you are looking for is spray booth quality.
As already stated filtering is needed at the fresh air intake.
Whatever volume of air you are trying to evacuate you need to replace and you want it to flow front one side to the other.
No matter what you do the exhaust fan system is no replacement for proper breathing protection.

[scmhogg]

Dan,

Be sure your fan is spray booth approved. The fire/explosion danger with a brush type motor has to be considered. A little lacquer thinner and .

Steve

[mschrank]

I've seen a lot of discussion in this forum regarding air cleaners, but very little about the point Dan brings up. As I am designing my new shop, I've often thought I would like some type of exhuast fan to use during finishing. I'd be interested to hear how you all deal with this in your shops.

I think Steve brought up a good point I hadn't considered. Until now, while doing finish work I've used a box fan in front of the open window to pull fumes out...probably won't do that anymore.

And sure personal breathing protection is the right thing to do, but I still want the fumes out. My garage/shop is attached to the house, and the LOML doesn't want to smell the fumes.

Mike

[maxparot]

My suggestion to anyone that is going to spray a large project for be to do it outdoors using a canopy with walls put a tarp in front and behind so any breeze will be blocked but air can escape easily.
I used this method to do a paint job on a car with great results.
Work shops make lousy spray booths!

[mschrank]

Moving the operation outside is a great idea, especially in Arizona . But in my part of the world I may have snow/rain/ice in winter and VERY windy conditions in summer (Hood River is well known to the wind-surfing community for this reason).

I don't mean to deviate from Dan's orignal inquiry about spraying, but this can really be extended to brushing some finishes. I try and stay away from the real high-octane stuff, but sometimes a project calls for a laquer finish. The fumes can really accumulate if you don't have a good way to exhaust.

Am I making this a bigger deal than it really is? I have not done as many woodworking projects as I would like, but I've done enough finish/re-finishing to make me wish I had access to that great finish room in my old high school woodshop!

[pierhogunn]

this application would be in a basement, that is unfinished, how would you isolate the basement from the rest of the house, ( there is no access fromt the house to the basement) some sort of vapor-barrier?

Dan

[Tom Miller]

Are there windows in the basement? I guess I would just put a box fan to exhaust out one window, and open another window for makeup air. Do your work close to the exhaust fan.

Regards,
Tom

[mschrank]

I made a "spray booth" in my garage using some fairly heavy sheets of clear plastic drop cloths (about 10'x10'), 1x2's, some eyebolts and hooks, and string.
-Attach two 10' 1x2's to opposite edges of plastic sheet.
-Attach one of the 1x2's to the ceiling.
-Repeat to make as many temporary "walls" as you need to enclose an area.
The temporary "wall" can be rolled up from the bottom when not needed. Run the string from an eybolt on one side of the roll to a hook on the other to secure the roll against the ceiling.

I have a hole cut in one of the "walls" near the window with the box fan. Turning on the fan creates negative pressure in the enclosed area and keeps fumes and overspray from the rest of the garage and house (and thanks to Steve's input, also likely creates an explosion hazard). I realize that this negative pressure likely also sucks in dust from outside the enclosure, but it never caused problems on my workpiece...maybe my workshop is just too clean & dustfree...LOL. I wouldn't want to apply finish immediately after sanding or cutting in the adjacent area.