How to Make a DIY Air Purifier

Last week, Oregon’s wildfires were the worst in the country. The ones burning are far from Portland, but smoke has a way of traveling. In September 2020, Portland had the worst air quality in the country. It’s a reminder that the months ahead may look, ugh, smoky.

As a precaution, here’s how you can make your own air purifier:

What You’ll Need

Gathering supplies may be the most complicated part for this simple project. You’ll need:

• A box fan, preferably square.
• A furnace filter: One that matches your fan; 20x20x1 is a standard box-fan size. It should be a high-quality filter, which means looking for one with a rating of MERV 10 or above.
• Packing tape.

Step 1

Tape the filter to the input side of the fan. (Note: most filters are directional, so check to make sure you’re sending the air the right direction before attaching.)

Step 2

Make sure to seal the edges of the filter to the fan, with tape, so that all air is forced to go through the filter.

• How-To Video: You can watch a New York Times Wirecutter reporter make a filter.

Next-Level DIY Purifier

The New York Times’ product review site Wirecutter found in one test that this simple fan-filter pulled 87% of particulates out of the air, performing better than some expensive air purifiers on the market. So there may be no need to go any further.

But a more elaborate DIY air purifier, called a Corsi-Rosenthal Box, was made to improve air quality during the height of COVID-19 and would also work for wildfire smoke. This style uses four or five high-quality filters, so it’s a good option if you don’t mind wrestling with a few more filters.

Here’s hoping none of this is necessary — but it may be worth getting supplies while they’re available.

Other Resources

Wirecutter reviews air purifiers, if you’re ready to make a bigger investment.