I grew up working in workshops that really didn't take health and safety seriously enough. As a result, I have some hearing loss and, find myself coughing at trace amounts of dust in the air. We put a small ceiling air filter system in when setting up the shop in 2019 to address that. It worked OK, but it was clear that a more aggressive solution would be better.
A few weeks ago, we started building another of our rolling workstation/storage carts. The overall design has evolved as we've built them out and we're getting to a really solid design we love. Each cart turns a 2ft x4ft space on the floor into a useful 6ft vertical use of that space.
The top half is generally all storage and the bottom half is a work table of some sort. When optimal storage is the goal, that table just gets more storage. In other cases, we're doing things differently. Which is where this project fits in. We decided to build a high flow air filtration system into one of these work tables.
You've likely seen DIY air filters made with box fans and furnace filters that folks were building to help with COVID air quality. And, if you watch many videos of workshop projects, you've seen a lot of variations on scaling that up a bit. But, most of those designs were less than ideal for our shop.
Many require a permanent solution up on the ceiling. That'd be great, but I'm probably only in this house for a few more years and need to be able to turn this all back into regular garage stalls for sale. Others put the fan so it pulls through the filters, but the exhaust blows things around in the shop. And, some folks flip that fan around, but then the fan motor gets covered in dust as it's exposed to the dirtiest air going through the setup.
The biggest issue I have with most of the designs is that they take up floor space without providing anything else. Flat working surfaces are one of those things you can never have too many of, so we decided to design a filtration system into a table. We put the fan in the middle, so it pulls through one set of filters and exhausts through the other set.
We used MERV 13 filters I already had, made it pretty much out of scrap 2x4s and some quarter sheets of plywood I also had, and the same with the casters that came out of our available stock. Pretty much all we bought was this Caterpillar fan that powers the whole thing and foam for seals
It's a relatively straightforward box, for the most part, with a solid plywood top and bottom. The sides have openings for the filters to slot in. They're held in place by wood strips screwed in place that press the filters against a lip installed behind and put foam seals on those surfaces.
The middle that houses the fan is the only thing that requires a bit more than a bunch of straight cuts. It's 4 plywood pieces that form 2 frames around the fan shroud. I cut 2 rectangles that fit exactly into that middle slot and then put 16" circles in that using the Shaper Origin to make one and a trim router to make a copy. At the edges, I cut so the fan could be inserted. Foam goes along the rim to form a good seal.
We clamped and put reinforcing blocks in place to keep that all from moving and it's remarkably solid without a vibration problem so far.
Based on math I found for another system that uses this fan, it could theoretically turn the air over in the shop every 3-5 minutes. Which, when you power it on, you can feel. You can tell that all of the air in the entire room is moving.
