DIY Project: How to Make a Box Fan Air Purifier

purpleair box fan air purifier

During wildfire season, ventilating our home can be a challenge. Opening the doors and windows could have a negative effect. Instead of letting in fresh, clean air, we can be letting in the air with a lot of particle pollution accumulation.

Furthermore, the air inside the house could also contain high concentrations of PM2.5 due to natural daily activities, such as vacuuming, lighting candles and incense, cooking, lighting a fireplace, etc.

People with asthma, allergies and respiratory problems can also experience trouble breathing if the air quality is not optimal. For this reason, air purifiers exist. Several brands and technologies can help you keep the air inside your house breathable. But unfortunately, most quality air purifiers come with a high price tag.

A convenient and equally powerful alternative is to make your own basic box fan air purifier. Here we will teach you how to make highly efficient air filter with an easy DIY project.

DIY Box Fan Supplies

For this project, you will need:

  • Box fan: You can use any box fan you already own or buy a new one. There are different options between $20 and $40; it is not required to have a timer, but you must ensure that your box fan is around 20 inches high (standard measure). Your local Home Depot or other hardware store will have many options with free delivery or pickup.
  • HVAC filters: Your filter's height should match your box fan. You can buy these filters also at Home Depot or purchase them online via Amazon. Remember to examine the Minimum Efficiency Reporting Value (MERV) rating. This rating will indicate the size of particles the filter is rated to capture. 
  • Duct Tape: This is optional, but it's a good way to secure the corners and prevent air leakage.
  • Bungee cords (2): Any bungee cord will do. Just make sure they actually stretch to the length of your box fan.

We recommend that you buy the filter which adapts better to your needs. Some models even have activated carbon, which is nice but is not a requirement. All filters will last up to 3 months in the box fan.

You should also know, the rating will indicate the size of particles the filter is rated to capture. For example, MERV 11 will catch all of the previously mentioned ones, plus pet dander, smoke, smog, cough and sneeze, and MERV 13 is the most powerful air filter. It will catch some types of bacteria and virus carriers.

box fan air purifier infographic

Once you have all the supplies, the first step is to unpack your filter. You will notice that this kind of filter has arrows that indicate the airflow direction.

Place the filter on the fan, make sure that the arrows are pointing towards the back of the fan. Once you are sure the filter is in the desired position, secure them with the bungee cords.

And that's it! You have done your own basic box fan air purifier. Make sure you change your air filter periodically. Once it begins to turn grey or has dust attached to it, it is a good sign that it needs a change.

If you are looking to step up your game and want to do a more complex project, we recommend this article on how to improve your box fan air purifier efficiency.

Air Quality Monitor & Box Fan Air Purifier: The Superstar Combo

Worried about air quality?

Monitor the Particulate Matter levels around the world with our free, real-time PurpleAir Map or join PurpleAir's mission to make air quality data accessible to everyone by investing in an air quality monitor for your home. 

Together, we can be informed and make changes in our daily habits and the community to improve air quality.