How many CFM

[Kardar2]

Hello,

I did a search and did a lot of reading but did not fingers a answer or I missed it. I  titled this post so someone might find it useful. So questions  if my paint booth is 3ft long and 2 ft deep. What size a fan (CFM) would I need? I saw post a guy had 6 ft long booth with 2 motors that pulled up to 300cfm so if I am guessing  I need 150 cfm? Thanks 

[rsxse240]

for an airbrush only booth, you really don't need that much, but if you're using spray cans a lot, you might make sure you get a good amount of cfm.  If you are pulling 150 cubic feet per minute, that is replacing the air in a 10'X10'X8' room in just about 5 minutes.  If you asked me, that's plenty sufficient for a 2x3x3 booth. The math tells me that your little booth would have all of the air replaced every .12 minutes or about 5 seconds.  That's pretty good.  

The main thing you'll want to consider when selecting a fan for your booth is what kind of paints you'll be using.  If you are going to be using an air compressor spraying water based paints, volatility may not be an issue, but if you are spraying lacquers, or other highly combustible paints or aerosols you will definitely want a spark free fan motor or sealed motor to lessen the chance of blowing yourself up.  not that I've ever heard of anyone blowing up in a freak airbrushing accident.  lol, it could happen!  

[Kardar2]

Okay thank you most far fans only get around 70 cfm.  So now I know what to start shopping for. 

[Aaronw]

It is the size of opening that matters, not area of the booth. A 2x2x2ft booth, requires the same fan as a 2x2x4ft booth, but a 2x4x2ft booth would require a fan twice as big. (HxWxL). It is not just CFM but also air velocity to push the fumes out, a big opening slows the air flow, just as a too small exhaust does.

This is a really good article if you want to build a booth comparable (or better) than one of the commercial hobby booths. 

http://modelpaint.tripod.com/booth2.htm

 

I've got a 2x2x2 ft booth, with a 485cfm squirrel cage blower. Factoring in the loss due to ducting (6" dia metal) it is around 400-450 cfm. Works great, including the blower I built it for about $200. Based on the article above I am right at the recommended flow for a 2x2 cross flow booth. Many of the commercial booths actually fall a bit short.

 

Grainger is a great source for shaded pole blowers (aka Squirrel cage), kind of a pain because you have to make an account, but good selection and prices, awesome service. I had my blower within 48 hours of making the order. Most of these blowers require a separate cord / plug since they are generally used as a replacement motor, a heavy duty cord is only $10 or 15 and easy to install.

 

Edited October 31, 2015 by Aaronw

[Kardar2]

Thank you for this info. This would be handy on a locked thread for newbies  like my self.

[Miatatom]

My booth is 2x3x3. I use a 135 CFM bilge blower I got off eBay for $15. Works fine!