Homemade Air Filtration System

Homemade Air Filtration System

Photo 1. My solution to cheap clean air in the shop.

Air quality is always an issue for woodworkers, especially if we are working in a basement or when we don’t want to give up the heat in the shop to an open window during those cold winter months. There are plenty of ‘store bought’ systems out there to filter the air, but they can be pricey. So for those of us who would rather spend the money on another router or just like to make ‘stuff’, I have a suggestion (Photo 1).

Homemade Air Filtration System

Photo 2. Just a box and an exhaust fan with a big hole in the bottom.

Build a box, cut a big hole in the bottom and install an exhaust fan in it (Photo 2). Then cover the hole with a couple of disposable furnace filters and cut slots in the bottom of the box to vent the filtered air back into the room (Photo 1).

Homemade Air Filtration System

Photo 3. I used metal-clad wire because of all my shop wiring is exposed.

Note: follow all local building and electrical codes when making, wiring and installing the system (Photo 3).

Homemade Air Filtration System

Photo 4a. The box is mounted between the trusses.

Homemade Air Filtration System

Photo 4b. I wrapped insulation around the box for good measure.

Homemade Air Filtration System

Photo 5. Only the filters and vents protrude into the room.

Now would be a good time to discuss a little air flow math: My fan is rated at 1000 CFM in 1600 sq ft of attic space, (cubic feet per minute) – that is how much air the fan will move in a minute. My shop/garage is 22′ x 22′ x 10′ = 4,840 cubic feet, 484 sq ft. So if my math is right, my fan should exchange the air in my shop in about 4 to 5 minutes. That sounds good to me.

I installed mine between the trusses in the attic, (Photos 4a and 4b) only the filters and vent deflectors protrude into the room (Photo 5). If you don’t have an attic, (or your mate won’t let you cut a hole up into the kitchen floor), just mount the box on the ceiling.

Homemade Air Filtration System

Photo 6a. The box measures 31". x 22". x 12".

Homemade Air Filtration System

Photo 6b. Close up of fan and shroud mounted in the box. I did have to bend the shroud base up on all sides to fit. The sheet metal cuts and bends easily.

My garage trusses are 24″ on center, so I was able to use a 15″. fan. The box measures 31″. x 22″. x 12″. high, (Photo 6a and 6b), and the base that mounts to the ceiling measures 32″. x 27″. I was then able to span the trusses and leave extra room for the vent slots.

Homemade Air Filtration System

Photo 7. I used two 1" furnace filters. When the bottom one gets clogged, I replace it and put the new one on top.

I used 2 filters to get better filtration, (Photo 7). I just replace the bottom one when it gets clogged and put a new one on top.

Homemade Air Filtration System

Photo 8. Notice the low profile in the shop.

Notice the low profile of the finished air filter in my garage. Good luck and breath deeply.

Photos By Author

Jake is a registered member of WWGOA. See more of Jake’s woodwork at his website, Saw Dust by Jake.

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11 Responses to “Homemade Air Filtration System”

  1. ericlsmith@outlook.com

    To what particle size are you filtering? 10 microns, 5 microns? To what particle size is enough? Thx, and I love the low profile aspect..

    • WWGOA Team
      WWGOA Team

      We did not perform a scientific study on this to determine the actual particle size that was captured, but because the exhaust in this case is blown into an uninhabited attic, the author was not as concerned with capturing the finest particles. If you are recirculating the air back into the shop or another inhabited space, it is more important. Ideally you would capture down to 1 micron or less in that case

      • moxonjim

        You apparently did not understand the design. The air is not exhausted into the attic, but is recirculated into the shop space. The box is closed on the top and air is sucked in through the filters and exhausted through ports on the ends of the box.

  2. William

    Looks good!. If you know a heating contractor, you might see if they have any old furnace blower assemblies they want to get rid of. They would be free (cutting your costs) and, if serviced regularly, would provide years of service. Also use Pleated filters rather than the cheap disposable ones. They are more expensive but will capture more dust too! Especially if you’re recycling your air.

  3. Bradley

    Hell of an Idea brother !! I Like it !! May have to “Copy” that…… Thanks dude !

  4. Jeff

    Your design looks as if the air from the work space is being sent outside and not back into the work space. In this case, the filters don’t provide any value to what you are breathing inside. In hot/cold climates, the cool/warm area is being sent outside increasing your cooling/heating bill. Also although the fan maybe rated at 1000 cfm, your design reduces this number, because of how close the top of the hood is to the fan and then has to may a 90 degree turn. In other words, the area flow is being pressed against the hood, stops and then moves towards the exit. My guess is that the design probably is working at 50 – 75% efficiency.