• How to Make a Room DIY Air Purifier

    Want to filter your indoor air, but don’t have an HVAC system or air purifier? These two DIY versions can help.

    Whether you need to clean your indoor air during a wildfire or filter out pet dander before hosting a guest, these DIY air purifiers made with a box fan and HVAC filters can help.

    • The DIY room air purifier trend is taking the internet by storm—and for good reason. Many people are looking for accessible ways to improve indoor air quality, whether your neighborhood is dealing with wildfire smoke or your classroom doesn’t get sufficient air circulation.

      If you can’t get ahold of a air purifier or you don’t have access to your building’s heating & cooling system, you can make a box fan room air purifier that’s backed by science.1 Here’s how you can make two effective solutions with box fans and Filtrete™ Air Filters.

      Corsi-Rosenthal Box room air purifier

      Different types and sizes of air purifiers can do different things—and the same rule applies when you build it yourself.

      Why use this box fan air purifier: A Corsi-Rosenthal Box combines four air filters and a box fan into a cube shape. DIYers often use them to capture unwanted airborne particles. And the best part? 3M scientists have found they are indeed effective at capturing tiny airborne particles, including viruses1. This can be a great addition to your current ventilation system if you’re looking to clean the air in a large room that doesn’t get much ventilation. Such spaces could include classrooms, offices, and nursing home living areas.

      Total time to build this box fan room air purifier: About 45 minutes.

      Total cost to build this DIY room air purifier: Between $80 and $100, depending on fan and filter choice.

      Filter change rate: Every six months (the same rate as a traditional air purifier). Filters will start to look dirty over time. That’ll be a visible cue for when it’s time to change.

      Materials needed to build this box fan air purifier:

      • (4) MPR 1900/MERV 13 20”x20”x1” air filters
      • Box fan (20”x20”)
      • Cardboard (20”x20”)
      • Duct tape
      • Cutting tool

      How to assemble this DIY room air purifier:

      1. Arrange the 4 Filtrete™ Air Filters in a square.
      2. Secure the Filtrete™ Air Filters together with Scotch® Duct Tape as you create the square. Seal the edges with ScotchⓇ Duct Tape between the filters.
      3. Place the fan on top of the filter square. Orient the fan so that the air is directed up towards the ceiling.
      4. Secure the fan to the filter box with Scotch® Duct Tape on all sides. Make sure to tape the corners as well.
      5. Create a shroud for the fan by cutting an 18-inch circle in the middle of the cardboard.
        • Please use adult supervision when using sharp cutting tools.
      6. Add shroud to the top of the box fan. The circle should be centered on the fan.
      7. Use Scotch® Duct Tape to secure the shroud to the fan.
      8. Plug the fan in, turn it on, and enjoy cleaner air!
        • Please use this device under supervision and turn the fan off when not present.

      Single-filter DIY room air purifier

      Why use this DIY room air purifier: Filtering with a 1500 filter or above helps remove large particles like pet dander and dust as well as microscopic particles like viruses. Its simple design and materials make it perfect for cleaning air in a pinch, but it has less filtration power than a Corsi-Rosenthal Box or a traditional room air purifier.

      Total time to build this box fan room air purifier: About 15 minutes.

      Total cost to build this DIY room air purifier: About $40.

      Filter change rate: Every three months, depending on how often you have the fan on. Since the filter is in plain sight and not hidden inside an HVAC system, you’ll see particles build up over time and get an idea of when it’s time for a change.

      Materials needed to build this box fan air purifier:

      • 20” x 20” box fan
      • 20” x 20” 1” Filtrete™ MPR 1900/MERV 13 air filter
      • Command™ Poster Hanging Strips, Small
      • Paper towels

      How to assemble this DIY room air purifier:

      1. Use a damp paper towel to clean the back of the box fan, ensuring it’s free of any dirt or dust. Let dry.
      2. Remove the red liner and apply Command Strips evenly around the back side of the filter. Note, apply the strips with the tabs facing outward for easy removal.
      3. Remove black liner from all tabs and gently press the filter onto the back of the fan. Ensure the arrow on the filter is pointing towards the fan.
        Hold for 30 seconds.
      4. Plug the fan in, turn it on and enjoy cleaner air!


      1. 3M scientists: “This Corsi-Rosenthal Box movement is legit.” 3M Company, 2022.
      2. IAQ Research-Practice in Action: The Corsi/Rosenthal Box Air Cleaner - Tex-Air Filters (texairfilters.com)

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