Normally, there’s not much of an air quality problem in my shop, since often the amount of dust that’s created is minimal. But during heavy cutting or sanding operations, it would be great to have an air cleaner that could effectively capture the airborne dust. Not only would it clean the air, but it would also help to keep the shop itself cleaner, by catching the dust before it settles.

The easiest way to make a low cost air cleaner is to just use a cheap box fan with a furnace air filter attached in some way to the inlet side. I wanted a more permanent solution, with a higher quality fan that is capable of moving a lot of air.
I started with a 20″; shrouded fan and used my giant calipers to measure the actual diameter of the shroud. I could then draw the circumference using my beam compass on a piece of 1-1/2″; foam:

I’m using foam for two reasons: first, it’s a lot easier to cut and fit around the fan than plywood. Second, it will help to absorb some of the vibration from the fan, making it less noisy.

I cut out the parts on the band saw, after cutting it in half:

I used silicone caulk to attach the foam divider to the fan shroud, and let it set for several hours:

While waiting for the silicone to set, I cut out the wooden parts. The bulk of the air cleaner housing is made from 1/2″; plywood, with some solid wood strips that hold the filters in place. The first parts to assemble are the “;L”; shaped pieces that the wooden strips attach to:

The narrow “;L”; has two strips spaced 1″; apart for one filter. The wider one has three strips, also spaced 1″; for two filters. I used a scrap of wood cut to 1″; wide as a spacer to fasten the centre strip in the right place:

I could them measure the actual width for the top and bottom panels (1/2″; plywood is rarely a full 1/2″; thick) and cut those to length. The top panel is fastened with glue and 1-14″; brads, then the shorter strips are attached to the ends of the longer strips in the same way. These create the opening for the filters to slide in:

The short strips are installed on the top panel as well, and that completes the inlet filter side:

The outlet filter side is assembled in the same way, attaching the “;L”; brackets, then the short strips.

With that done, I could get the foam divider glued in. I used silicone again to attach it to the top and bottom panels, with temporary spacers to keep it in the right place:

The narrow bottom panel is glued and clamped between the inlet side and outlet side, the the side panels are installed to close the unit. Again, I used silicone on the foam, and regular wood glue and brads to attach the side panels.

I notched one of the side panels for the fan cord to come through, and notched the mounting cleat as well:

The unit can be free standing, hung from the ceiling, or mounted on the wall like I did:

I decided to place mine on the wall beside the band saw, below my camera gantry track.

In this location, there’s nothing to impede the air flow:

With the filters accessible from the end, removing them for cleaning and replacement is very convenient. I plugged the fan into a remote control outlet that allows me to turn the air cleaner on from anywhere in the shop. Ideally, I’d like it to come on whenever I turn on a tool, then run for 10 minutes, or so, before turning off. Possibly a sound activated timer would be an interesting project to make that possible.

This detailed video goes through the build from start to finish, and shows the air cleaner running: