Any DIY Paint Booth Filter Recommendations?

[danthefisherman]

Hi TU,

Trying to take steps to make the shop safer health-wise and am in the market for a paint booth filter for a 20"x20" box fan. I'm trying to determine what MERV rating will maximize flow & filtration with minimal cost. Obviously the finer the filter the higher the cost, but I'm not sure if a MERV 4 fiberglass filter will suffice for painting baits. Furthermore, my box fan may not be strong enough to pump enough air through a MERV 12 regardless (?). Maybe a MERV 8 is a good in-between option?

Any recommendations would be much appreciated as this is all new to me. TIA!

Linked below is an example of what I'm looking to make to catch air brush overspray.

https://www.youtube.com/watch?v=9vJk5BM8xUo

[hazmail]

Hi Dan

Not sure if paper filters would be the best option for paint.

I know there are a lot of people using them but as you say the motor H.P requirements need to be big . 

The problem with paper /fiber glass is paint tends to dry/ or "set" very quickly when blasted with air (especially thinners based paints), so it will quickly start blocking the filter which restricts the air flow which allows more paint to set in the filter, so around and around it goes and probably starts drawing air around the filter or from the back.

Lots of guys use "flash proof" Gas Heater fans from old home gas heaters. The overspray is transferred (suction) via a spray booth (box) into corrugated plastic or Al (heater ducting) ducting along which it travels through the fan (squirrel cage heater fan) and out to the atmosphere.

If you use enough flexible ducting (4" or Bigger) the paint solids tend to set in the ducting, not the fan blades, the solvents or water will be expelled through the fan- which MUST BE FLASHPROOF. Connect the ducting via PVC pipe fittings.

Bash the ducting occasionally and the paint solids will fall off as paint dust. Had one for years and still works as new, still passes the required air volume tests too. Pete

 

[mark poulson]

15 hours ago, hazmail said:

Hi Dan

Not sure if paper filters would be the best option for paint.

I know there are a lot of people using them but as you say the motor H.P requirements need to be big . 

The problem with paper /fiber glass is paint tends to dry/ or "set" very quickly when blasted with air (especially thinners based paints), so it will quickly start blocking the filter which restricts the air flow which allows more paint to set in the filter, so around and around it goes and probably starts drawing air around the filter or from the back.

Lots of guys use "flash proof" Gas Heater fans from old home gas heaters. The overspray is transferred (suction) via a spray booth (box) into corrugated plastic or Al (heater ducting) ducting along which it travels through the fan (squirrel cage heater fan) and out to the atmosphere.

If you use enough flexible ducting (4" or Bigger) the paint solids tend to set in the ducting, not the fan blades, the solvents or water will be expelled through the fan- which MUST BE FLASHPROOF. Connect the ducting via PVC pipe fittings.

Bash the ducting occasionally and the paint solids will fall off as paint dust. Had one for years and still works as new, still passes the required air volume tests too. Pete

 

Pete, does the ducting need to be grounded?

[hazmail]

Hi Marc- You would think it would,,, as its that collapsible AC ducting 4".

As with PVC tube, some say yes, others say it's all B/S- I suppose to be on the safe side it wouldn't take much to do, never been zapped yet, but if it exploded it would be a drama. You probably remember I built this one years back and have added 2 more tubes since, which works much better--

Its a "downdraught" set up, air is drawn down then up through the 4 tubes to the "Fan Box" and then expelled outside, through the shed wall.

 

 

[mark poulson]

9 hours ago, hazmail said:

Hi Marc- You would think it would,,, as its that collapsible AC ducting 4".

As with PVC tube, some say yes, others say it's all B/S- I suppose to be on the safe side it wouldn't take much to do, never been zapped yet, but if it exploded it would be a drama. You probably remember I built this one years back and have added 2 more tubes since, which works much better--

Its a "downdraught" set up, air is drawn down then up through the 4 tubes to the "Fan Box" and then expelled outside, through the shed wall.

 

 

I always used metal ducting in my home shop dust extraction setup, so I knew it was grounded.  I know house dryer venting is typically PVC, or the same flex duct you show, and neither is grounded.  I was always leery of ungrounded ducting in woodshop extraction systems, because dust explosions were a real danger when I was young, so I'm probably overly sensitive about the need for grounding.

[hazmail]

Yeah, I remember the U.S was famous for a few Silo explosions (wheat dust etc).

They used to show them to us at work quite a lot. Wouldn't like to be there, pretty spectacular though.

[danthefisherman]

@hazmail thanks for the input and nice setup!

Sounds like I have a bit more researching that I need to do, but until then I already have a cheap box fan and MERV8 furnace filters on the way.  I’m going to make a mock up cardboard spray hood to help catch overspray and direct it into the filter, and if I like it then I can remake another out of more robust material.

I do want to eventually have a ducting system to exhaust everything outside, but anything is an improvement to what I have now (basically nothing). I use Createx airbrush paint which I think is water based and hopefully less of an explosion risk than solvent/oil based paints.

[mark poulson]

10 hours ago, danthefisherman said:

@hazmail thanks for the input and nice setup!

Sounds like I have a bit more researching that I need to do, but until then I already have a cheap box fan and MERV8 furnace filters on the way.  I’m going to make a mock up cardboard spray hood to help catch overspray and direct it into the filter, and if I like it then I can remake another out of more robust material.

I do want to eventually have a ducting system to exhaust everything outside, but anything is an improvement to what I have now (basically nothing). I use Createx airbrush paint which I think is water based and hopefully less of an explosion risk than solvent/oil based paints.

Just remember that dust is explosive, and water-based paints create dust when they dry.  So buying more expensive filters might actually work against you, because you'll be more hesitant to change them as often as you should.