Wednesday, September 14, 2011

Shop Filter Blower

Filter blower is 12"x24"x30"

I received a filter blower kit from PennState in 2006 as a present and it has been sitting on a shelf in my shop ever since. PennState no longer sells this kit, but does sell a complete unit for $299. plus shipping as the AC620. Because I have recently been working with MDF, I decided it was time to build the kit. (Note: This filter does not eliminate the need for a face mask will working with MDF.)

Since the kit is no longer available, this project is presented as a complete construction project with a full set of parts which can be purchased thru Grainger, PennState and other vendors. The cost of this project should be around $200 with the biggest cost being the blower ($90 to $120).  Check the surplus houses using Goggle for possible substitutes. I found the Dayton 1TDR9 on Amazon for $120. delivered.

MDF produces a fine dust during routing, cutting and sanding requiring the use of a filter mask. The dust particles generated are about the same size as when sanding pine; however, MDF contains formaldehyde. Some of the particles created are sub-micron which can stay airborne for many hours and can be inhaled and imbedded in lung tissue. If you will be working with MDF the bag filter used in this project should be a MERV 14 such as the Grainger, 6B660. The PennState came with a MERV 12 filter which will not extract sub-micron particles from the air.

Filters are rated based on their ability to remove particulates from the air. The American Society of Heating, Refrigerating and Air-Conditioning Engineers has defined the MERV rating system for filters. A HEPA filter in this chart corresponds to a MERV 15 or better. For our purposes we have chosen a MERV 12 as a prefilter and a MERV 14 as the post filter. This combination should do a good job of sweeping the shop air of unwanted particles at a reasonable cost ($50.) which will be good for us and finishing projects. Remember as the prefilter loads up the back pressure on the fan will increase lowing the CFM  and increase sweep time.

If you have a small shop and do not which to build this project you might investigate Shop Fox W1746 which can be purchased thru Amazon for $100. This unit claims to remove 0.3 micron particles and has 200 cfm air flow which should cycle a 10ft by 10ft shop every 5 min.

If you like quiet in your shop when you are not running tools, then this is probably not the filter blower for you, since the squirrel cage blower is noisy. A better design would use a reverse impeller fan such as the EBM R2E220-AA44-23 and sounds like a great project for the future.

Finally, before we start building, if all this information about sub-micron particles and lung damage has you freaked out, then you might be interested in a low cost particle counter, the Dylos DC1100 PRO with PC interface for $290.


  1. 2 pieces 1/2" plywood 30" x 23 7/8"
  2. 2 pieces 1/2" plywood 30" x 12 7/8"
  3. 1 pieces 1/2" plywood 23 11/16" x 11 11/18"
  4. 4 pieces 3/4" x 3/4" poplar, 25 3/8"
  5. 4 pieces 3/4" x 3/4" poplar, 10 1/4"
  6. 4 pieces 3/4" x 3/4" poplar, 23 3/4"
  1. Blower: Dayton 1TDR9
  2. Bag filter: Grainger 6B677 or Pennstate Ind. AC655
  3. Pre filter: Pennstate Ind. ACPF, (24" x 12" x 1/2")
  4. Electrostatic: Pennstate Ind. ACES1224
  5. Switch: Mouser # 540-SRB22A2FBBNN
  6. Power Entry Module: Mouser # 562-723W-X2/03
  7. Wire: 18 gauge hookup
Alternate Filter
  1. Pre filter: 24" x 12" x 1" ( Lowes, etc.). Use this filter with bag filter. A standard filter should be about 23 1/2" x 11 1/2" x 3/4". The opening in the box is 23 7/8" x 11 7/8" using 1/2" plywood. 
Plywood: For this project I am using Sandeply from HomeDepot, but birch will also work. I had HomeDepot cut a 4' x 8' sheet of 1/2" Sandeply into three pieces, two being 31" x 48". By the way, Sandeply is not 1/2" thick, but 15/32".

Construction Steps:

  1. Cut all the plywood panels to size.
  2. On the inside of each panel, mark the positions of the 3/4 x/3/4 cleats. The cleats for the filters are positioned 2" from one end and the fan plate cleat, 5/8" from the other end.
  3. Rather than use clamps and glue to assemble the box, I used Kreg micro block and pocket screws with glue. In the photo below, you can see that one of the box sides is held vertical using the jig shown. Wax paper was used on the bench surface to prevent the pieces from bonding to the bench.
  4. Once the box is assembled, glue the cleats in place.
  5. Using a router with a 1/2" end mill cut the holes in the fan end plate. To accomplish this a template was made using scrap lumber and Kreg pocket screws. See photo.
  6. Once the holes are cut in the fan plate, drill all the mounting holes.

    Construction photo set:

    Dayton 1TDR9 Blower

    Inside view  of box side panel where lines indicate position of cleats.

    Jig for holding the box side in place. Wax paper on bench surface.

    Shows pocket screw for assembling and gluing sides.

    Gluing filter cleats in place.

    Struts used to hold corner cleats in place during gluing.

    Template for routing fan hole

    Switch plate milled on Sherline

    Fan and switch plate mounted and wired

    Fan mounted in box

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