Exhaust fan for spray booth

[Peter M. Spirito]

Lets say I build a small open front spray booth large enough to spray an end table sized project. And I will only spray water based laquer, stains etc. Only water based products. On the back wall of the spray booth is a couple of rows of very good quality air filters. Any reason not to just hook up my dust collector to the back of the spray booth? A straight shot from the dust collector to the spray booth and also have an extra bag to use on the dust collector that I would put on only for spraying.

[Matt Meiser]

The fan I bought is something like 6000 cfm. I don't think you'll get enough air movement from a dust collector.

[Ken Fitzgerald]

IMHO I don't know that I'd want to pull the fumes into the body of my DC. Overtime I think a build up of residue from spraying could have a horrific effect on the operation of a DC. Just MHO.

[Frank Chaffee]

Peter,
Good question, and as Matt has pointed out, a dust collector or cyclone will not move enough CFM of air to evacuate an open faced spray booth.

I will suggest that a spray booth with an opening gauged to the capacity of the DC system will prevent overspray from getting back into the shop.

Matt said in his spray booth thread that his filters removed all visible mist from the air drawn thru them. Some water puddled on the floor when he tested with a direct overload of spray. Would enough moisture be removed during normal spraying to safely pass through a cyclone type dust collection system without damaging either the impellor or the filter? Are filters available that would allow this, or would it be necessary to bypass the filter side of a cyclone?

If we could retain conditioned air in our shops when spraying, we could save $.

Frank

[Shaun Wilson]

A dust collector will not work very well at all for this - wrong type of fan. Dust collectors and their fans are designed to move the air through a relatively small pipe (say 4-8" for arguments sake) at high speed (4000+ feet per minitue (FPM))and under higher static pressure (SP). A spray booth does not need to move the air very fast (100 or so FPM velocity at the face) but needs to move a huge volume (CFM) because of the large area of the opening, and operates at much lower SP than a dust collector. For a homemade booth, I think a carpet drying fan or similar would be a much better choice. I googled "carpet dryer" and found several from $100 and up. I have seen them for sale used and in fact bought one several years ago for $10 at auction and it really "blows";). My only caution is that you don't want to spray anything volitile or solvent based with a home-made booth. The risk of fire or explosion is very real. For anything that could burn or explode, you have to buy a real booth, or professional plans for constructing one. The NFPA 33 Standard deals specifically with spray booths and their construction. You can find a lot of useful info by googling "nfpa 33", although the actual standard must be purchased.
Hope this helps,
Shaun

[Peter M. Spirito]

Everything you guys said sure made sense. Thanks for the imput. You covered all of the possibilities.