My cats' litter box makes a lot of dust. One way to capture the dust is with a store-bought air purifier. Ever price one of those department store air purifiers? Some of them run upwards of $100. And the filters? Well, if you think replacement razor blades are expensive, you don't want to know about replacement filters.
So I made my own air purifier out of a cheap fan and a cheap furnace filter. Here's how...
Step 1: What You Need
* Squirrel-Cage Fan - $22
** Air Filter - $8
* Standard rotary fans don't work as well. Plus, it's harder to cut a circular piece of filter.
** You pick how much filtering power you want by choosing the quality of the air filter. You can get different MERV ratings. Spun glass filters don't work; forget those. Pick a filter height that matches the height of the air flow openings in your fan.
Step 2: Open Up Furnace Filter, Cut to Size.
This is the hardest step, which isn't very hard. Carefully open up the cardboard frame of the filter. It's glued in a number of places and is not meant to be opened, so take your time and don't mangle the filter element.
Keep the wire mesh frame; it's too hard to remove.
Stretch-out the pleated filter so it is flat. I used the edge of a table to straighten each pleat.
Cut a piece that completely covers the back air flow opening on the fan. Use old scissors - they will cut through the wire mesh but will damage them slightly. Using wire cutters on the mesh only for a first-pass will work too. Then use scissors to cut the filter itself.
Step 3: Duct Tape Filter in Place
All that's left to do is duct tape the filter in place over the back of the fan. Be sure to overlap the air flow openings so that there are no holes through which the air flow can bypass the filter.
That's it! I use mine to filter cat litter box dust. A store-bought air filter would get plugged up in a couple weeks. If a store-bought filter is $25, I can get 4 filters from one furnace filter that costs $8. That's >12x savings on the filters!
And no custom filters to go obsolete on you!
The squirrel cage fan is quiet on low speed, so it doesn't flip out the cats.
Hope you (and your cats) like it.
(OK, the cats couldn't care less...)