Air cleaners — or “air purifiers” — are expensive for what they are, which is typically a fan with a filter or series of filters inside a vented plastic box. Beyond the initial investment, you need to either buy unreasonably expensive replacement filters designed for a specific unit (think printer ink cartridges) or wash a reusable filter that’s not as effective.
It’s allergy season here in Seattle, and double-dosing on Claritin (actually, generic Loratidine, which is identical but an order of magnitude cheaper) doesn’t seem like something I should make a habit of. So, after spending far too much time reading reviews and pros/cons of different units ranging from $50 to $300, it occurred to me that I could easily build something that would get the job done with household items I already had and a commodity furnace filter.
With just a few minutes of work and a $15 investment on top of the $15-$20 I’d already spent on a 20″ box fan, I had a very effective and reasonably quiet air purifier for a fraction of what I’d have had to spend on a commercial product to move a similar volume of air (e.g., this model by Whirlpool). A nice savings, not even counting the fact that my filter could be swapped out for about $15 vs. $100 or so for essentially the same thing on the commercial purifier.
The build is very simple:
- Locate your 20″ x 20″ box fan, or purchase a new one
- Buy a package of 14″ (or longer) zip ties
- Buy a 20″ x 20″ furnace filter with a MERV rating that suits your needs and price range
- Place the filter on the back of the fan, ensuring the airflow arrow on the filter faces the back of the fan
- Poke a zip tie through each corner of the filter and through the fan, and zip tight at the back of the fan
- Enjoy your clean air!
