Box Fan Dust Filter

[Alfred Hoffmann]

Although I have a pretty good DC system including a ceiling mounted Air Filtration System I find that sometimes sanding small parts it pays to have a dust collector near by. That in addition of wearing a face mask. So I recently built a box fan dust filter the design of which I found in an old Woodsmith magazine from June/July 2007. I basically employs a box fan with a couple of furnace filters mounted in front of it. Since I am more and more allergic to wood dust every little bit helps.

[David Hostetler]

Certainly prettier than my job of simply duct taping the allergen filter in place...

I put mine on the intake side, and sealed up any errant holes in the housing with, you guessed it, duct tape...

I am digging around for a used relatively high CFM squirrel cage fan to use for a full on air cleaner... Brand new they are kind of spendy.

[Peter Aeschliman]

Very cool.

How well does it work? How did you go about selecting which filters to use??

Obviously you could go nuts and get a MERV 16 rated filter, but I have no idea whether a standard box fan could handle that level of resistance and still move enough air to make it worth it.

Do you also use a downdraft table? If not, what made you chose this approach rather than doing a downdraft table?

[Alfred Hoffmann]

Peter, I just bought standard 20 x 20 furnace filters. The box fan is a 3-speed fan bought at a local HW store. I use it with the highest speed setting. Obviously the suction is greater with only one filter in place. I am mostly concerned with the very fine dust generated when I use 220 or higher grid paper. The best way to check how well it works is to let smoke be sucked through the filter. I did this test in the garage so as not to set the smoke alarm off.
I do use a down draft box as well when a lot of sanding is required. The down draft box is hooked up to my DC system.

[harry strasil]

window fan, slide in from side furnace filter.

http://img.photobucket.com/albums/v81/irnsrgn/wood/aircleaner01.jpg

http://img.photobucket.com/albums/v81/irnsrgn/wood/aircleaner02.jpg

#2, both hang from the joists with french cleats.

http://img.photobucket.com/albums/v81/irnsrgn/wood/shpairclnr010.jpg

http://img.photobucket.com/albums/v81/irnsrgn/wood/shpairclnr011.jpg

They are on the shop lights circuit, when the lights are on the fan/filters are on automatcally.

[Andy Gilbert]

Good idea - though getting the dust before it becomes airborn is much more effective. Your photo shows that you are not using your sander with a vacuum. I believe Ridgid has one that's 6 HP for about $100 at HD (yes - I know the HP rating is dubious but look at the cfm rating - its very good - don't be tempted by the lower HP machines - get the biggest you can) and replace the filter with a Clean Stream HEPA filter - they are about $35. Not only are they superior filters - by far the best bang for your buck you can get - they last forever and are very easy to clean since they have a teflon coating. Then attach the vac to a Oneida Dust Deputy mini cyclone (around $60), or a Clear Vue mini cyclone (pricey at $135) or build a Phil Thien baffle using a 5 gallon bucket (search on his name here - there are many posts and he has his own website). This will separate 99% of the dust before it gets to your vac so the filter does not get clogged and truely performs to HEPA standards. Finally, replace the pad on your sander with the Abranet system from Mirka Abrasives. They are sanding screens that allow a vac equipped sander to remove virtually all sanding dust before it becomes airborn. They are simply fantastic if you want to eliminate sanding dust. Dust pick up from regular sanding pads with the 5 hole or 8 hole patterns is very good too but doesn't compare with how the Abranet works. Then use the same set up and attach to your router etc. Your lungs will thank you and your shop will be cleaner. Cheers

[Larry Browning]

I am digging around for a used relatively high CFM squirrel cage fan to use for a full on air cleaner... Brand new they are kind of spendy.

SOMETIMES (not always) HVAC companies have these things laying around their yard that they would be willing to give away, rather than sending them to the landfill. I got one that has a 220V motor. These can be replaced with a 110v motor for $40 - $60 if you look on line. I will be doing this with mine when the time comes to make my sanding table. I have several projects in line before this one though, so it will be a year or so before I do it.

[glenn bradley]

+1 for a vac hose . . . amazing difference.

[Myk Rian]

A suggestion for anyone making one of these. You will have much better filtration if the fan is drawing the air through the filter, instead of pushing it through. A partial vacuum creates far less leaks, and insures that the dust will be drawn through the filter, instead of being pushed out of openings. The same reason your home filter is on the upstream side in your furnace.

[David G Baker]

Myk,
That is what I would do, put the filter on the draw side as you suggested, that way the dust doesn't flow over the motor as well.

[harry strasil]

Plus it keeps the fine dust outa the motor and off the fan blades so it will move air.