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How to Make Your Own Air Purifier

Posted on May 20, 2024   |   Updated on September 30, 2025
Adrian González

Adrian González

Washington Post health reporter Lena Sun shows the steps in making a do-it-yourself box fan air filter, also known as the Corsi-Rosenthal Box, on December 21, 2022 in Washington, DC.

Air purifiers can cost you hundreds of dollars but you can make one at home with a few items from your local hardware store. (Michael Robinson Chávez/The Washington Post via Getty Images)

Madisonians recently got their first air quality alert of the season. With wildfire smoke blowing in from Canada, keeping your lungs safe from harmful particles is crucial. Air purifiers can make a huge difference when it comes to indoor air quality, but they can be expensive, so here’s how you can make your own at home with a few simple items.

🧰 Quick and Simple

Necessity is the mother of invention, so let’s start with the most simple version of a DIY air purifier.

  • Step 1: Acquire a square fan (most air filters are squares or rectangles, so we’re applying basic geometry).
  • Step 2: Get yourself a HEPA filter (shoot for one similar in size to your fan).
  • Step 3: Secure the filter to your fan via duct tape or packing tape, making sure to seal the connection as tightly as possible.

▶️ Follow along with this tutorial from the New York Times’ Wirecutter. Their testing showed this simple version outperformed a fancy $800 air purifier!

👷 Take it to the Next Level

After covering the COVID-19 pandemic, The Washington Post reporter Lena H. Sun took it upon herself to build what’s called a Corsi-Rosenthal Box, which basically takes the version above and gives it superpowers. She has a great step-by-step guide on how to build one.

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