Air Filtration Unit #3

About a dozen years ago, I decided to build a TV console to help de-clutter the various devices feeding our television. It wasn’t meant to be a super nice piece of furniture, mainly because I decided to build it mostly out of scraps of various species of wood I had on hand. Except for the top – that would be from a really nice piece of wenge I obtained years earlier for a project that never came to fruition. The basic design came from an article in a woodworking magazine:

Here’s a few photos from the build:

And the finished product (probably should have dusted the top before taking the photo):

So that’s the starting point for this latest air filter project. In an earlier post, I detailed how I built an end table filtration unit using an ultra quiet bathroom fan and a 12 x 12 near-HEPA filter. That worked out pretty well – we get a lot of wildfire smoke in central Oregon. In the bedroom, I’ve been using the first filtration unit, which is a stand-alone piece that doesn’t double as a piece of furniture. But, although it probably works better than the end table unit because of its larger filter (12 x 24), it’s kind of ugly. We’ve moved since I built the TV console and it now serves as an end of the bed … cabinet, table, whatever you call that sort of thing. A couple of months ago, I was staring at it (and I think I will just refer to it as a TV console) and thought that we really didn’t use the four baskets that sit on the lower shelf all that efficiently. And I looked at the ugly filter unit. What if I replaced two of those baskets with a fan & filter and installed a door? Yep, I’m doing it.

I’ve learned a bit from the first two filter projects (the ugly one and the much nicer end table) so installing the fan and filter in the TV console went a lot smoother. The challenges are two-fold. First, I had to figure out how to orient the fan so the exhaust port points in a direction away from the filter – doesn’t do any good to promote a circulation loop – and where I could easily breach the side panel of the console. The other units had four inch dust collection fittings installed to accept a hose. This one would just exhaust directly out the side with no hose. Second, I had to figure out how to mount a filter so it could be replaced easily. The first unit – with the bigger 12 x 2 filter – kind of failed that criterion as it requires removing several screws to get at the filter. The second unit – the end table – has the fan sitting horizontally with the filter resting on top in a custom frame. Very easy to change out by opening the louvered front door. The TV console couldn’t use either of those configurations. The depth of the console is less that 12 inches, so the fan had to be aligned vertically and the 12 x 12 filter had to be angled to fit. Took a little experimentation but I think I managed to nestle both inside the console nicely. The air is drawn from the right side where the two remaining baskets sit, and is exhausted through a port in the left side. There’s a screen covering the port. As with the end table unit, along with an on/off switch, there’s an electrical outlet for convenience. Not sure what we might plug in but it’s there.

There was actually a third challenge, one I couldn’t manage quite as well. Because the TV console was built with several species of wood, I tried to get them all to ‘blend’ by using a dark stain. Either black cherry or walnut, I forget. It worked out OK, not great. But now I was adding a front panel door of yet another species. And as I mentioned, I couldn’t remember the stain I used. The final result is also just OK. Given the bedroom is usually fairly dark , it’ll do.

The filter is easy to change. Two strips of wood are dado-ed to loosely accept the filter and I installed weatherstripping front and back to seal it in fairly snugly. A wooden dowel holds the filter against the rear weatherstripping and the door latch is set to seal the front weatherstripping against the filter frame. Just open the door, pull the dowel and slide the filter in or out. All the other avenues of air leakage are sealed as well, so essentially all the air drawn through the fan goes through the filter and out the exhaust port. A little might leak out around three sides of the door but not much.

The finished product:

Having the console down in the woodshop opened up the bedroom a bit, so I decided to place the finished piece against a wall until we need it. It’s easy enough to slide it over the the end of the bed when the air quality gets bad, as it inevitably will again next summer, and the summer after that.

Next up, a filtration unit for my neighbor. When the air was really bad this year, I quickly cobbled up a fan-filter for her to help alleviate headaches and such. Her unit will essentially be a copy of my end table piece, sized to fit.

Project: Air Filtration Unit

Years ago, I built a portable air filter to help with allergens in the house. It isn’t much to look at but it moves a lot of air. Basically a 1 ft x 1 ft x 2 ft box, it has an ultra-quiet bathroom exhaust fan inside that draws air through a standard home air filter in the front and pumps it out through a 4 inch port on the side. From there I can attach a dust collection hose to pipe the air to the other side of the room to promote circulation. Other than the on-off switch, that’s it. And the unit has worked well – it’s still quiet and based on how quickly the filter dirties up, it’s effective. Pretty ugly though – because I made it out of scrap wood, it needed to be painted instead of a nice wood finish. Not sure I chose a good color.

I decided to build another one but this time, it would be more of a piece of furniture and better looking. More of a woodworking project. After considering our needs, we decided the air filter could be a sofa end table. The current table is too small and too low. I’ll cut the suspense and show the final result now.

Same basic setup: an ultra-quiet fan drawing air through a standard filter and piping out through a 4″ port. This time though, the filter would be wholly inside the cabinet, smaller (12″ x 12″), and would draw air in through a louvered door. After playing around with fan orientation, I settled on having the filter on top with the fan mounted horizontally. That setup would allow room above the fan/filter for two narrow drawers. Additionally, because it is meant to be an end table, along with an on-off switch, I installed an electrical outlet to accommodate a tabletop lamp.

I like to use the wood I have on hand for projects if I can and I had a sufficient quantity of white oak, so that’s what I chose. For the side panels, which are 1/4″ plywood, I bought some white oak veneer. I had not used veneer before so that was new.

Mistakes were made. The biggest being a failure to properly account for the four vertical posts when I did the top piece, which was made from the best, most attractive cut of wood. The top turned out to be too small so I had to use other pieces to make a bigger one. The first top piece ended up being cut down for use as the two drawer fronts. The next biggest mistake was a goof in installing the door. The louvers ‘point’ up instead of down. That’s not so bad – it may even be beneficial in terms of drawing air from the room rather than the floor. But it wasn’t what I had intended.

Here’s the new top. I failed to take a photo of the original.

And some miscellaneous build photos.

One final note. This summer, Oregon had horrendous wildfires, as did Washington and California. The air quality in my town reached and stayed at ‘extremely unhealthy’ levels for a long while. Because I use near HEPA filters in my units and the house’s FAU (forced air unit), they’re effective at capturing smoke particles. So along with the FAU and my first portable unit, I pressed this new one temporarily into service before the cabinet was complete.