shop exhaust fan placement?

[hobby67stepside]

I first posted this on paint and body but there is so much more action here I'm going to ask again. My shop is about 40' x50' and 16' sidewalls. Fully insulated and lined with steel. I need an exhaust fan and wonder where I should place it - closer to ceiling or closer to floor. It will be close to a corner and I have windows on the opposite side I can open for air inflow. Does paint tend to move upward or drift down with gravity? What painting I have done in my shop seems to go everywhere throughout my whole shop!!!!!!!

[ozarkhippie]

It needs to be placed closer to the ceiling to get out smoke and exhaust. But a friend of mine who has been in the body shop business for a very long time says the ideal placement (his opion) is near the floor in the paint booth. He says it pulls the overspray down and keeps the dust on the floor rather than having a fan up high lifting the dust ect up causing it to get into the paint.

[hobby67stepside]

That makes sense to me. You wouldn't want to lift up the dust and dirt from the floor. I know of a body shop where the fan is low and I wondered if it was the only place it could be or if it was there for a reason. Now I think I know. Thanks.

[ozarkhippie]

Another thing that I learned is to create a static pressure by leaving the doors and window open only by a inch or so, it will move more air rather than completely opening them. I don't have a paint shop but we weld and repair alot in mine. I have a large 3 foot fan mounted in the peak of the ceiling.

[hobby67stepside]

I do a lot of welding and maybe I should be concerned about those fumes, but my main concern is the paint. I made the mistake of painting my frame last winter with an enamel (not that it's a mistake to use that paint) but that it floats around a lot before it dries and it darkened my nice white interior, and that's what I don't want to get even darker. I think had I had an exhaust fan in then, I wouldn't have made my nice white interior a little darker.

[ChevLoRay]

....and you may want to install two fans. One, down near the floor to minimize the dust, as stated in the other posts. The other, you may want to install in a gable to help rid the shop of heat and vapors that may rise to the ceiling. Just a thought. You know what you need.

[hobby67stepside]

Thanks for the input. These replies will help me decide.

[Low69CST]

my dad has about a 20 x 17 x 10 (tall) paint booth. we have the fan center of the floor, it pulls down and through hole that runs under the shop and out the side. Try to keep the fan as center as possible to pull the fumes evenly. Also, make sure you line any ventalation sources with filter. If not you'll be suckin in dirt and insects like crazy.

[lost wages]

i built a small room for sandblasting in my shop and put the fan about in the middle of the wall, i only have ten foot ceiling though, it is direct drive and pulls alot of air.

[Jwill41]

I work for a paint booth manufacturer and we like the downdraft approach. Be careful of sparks from the fan motor. The motor should not be in the air stream for explosion reasons.