DIY Air Filter

One easy and affordable way to make your own air cleaner at home is with a box fan and a furnace filter. These “filter fans” can filter out the small particles that are common in wildfire or wood smoke. Particle pollution can lead to a number of immediate and long-term health impacts such as trouble breathing, asthma attacks, and lung and heart disease. Particle pollution is especially dangerous for children, the elderly, and people with sensitive immune systems.



We have tested the performance of these filter fans and they dramatically reduce fine particles and black carbon from the air. See the graph below that shows an example of the filter fan performance.  

Filter Fan Performance

Supplies you need to make your own:

  • 20" x 20" box fan
  • 20" x 20" x 1" MERV 13 or FPR 10 filter 
  • Power drill*
  • 3/4" screws*
  • 2" corner brackets*

* If you do not have access to a power drill, you can simply use any kind of tape or a bungee cord instead of screws and brackets.

All supplies can be found at home improvement or hardware stores.


See the video tutorial on how to build a filter fan yourself:

The video was made possible by the students from RecTech, an internship program with Seattle Parks and Recreation. RecTech’s mission is to remove barriers and train students through technology to better prepare them for college. 


Important Tips While Installing Filter to the Fan: 

  • Make sure the filter is placed against the back of the fan.
  • Make sure the arrows on the filter point towards the front of the fan or follow the same air flow of the fan.


Important Tips While Using Fan:  

Box fans were not designed for use with filters and the safety of filter fans has not been tested. Be sure to follow these instructions:

  • Use the fan in the room you spend the most time in.
  • Position the fan toward the middle of the room, away from walls and big objects. Do not position the fan near a dusty or dirty area or the fan will blow the dust into the air.
  • Close all windows and doors while fan is in use. The filter fan can’t clean the air if outside pollution is reentering the room. However, if it is too hot inside you can open a window and run the fan without the filter.
  • Use the fan for at least 10-15 minutes when needed.
  • For electrical safety, do not use the fan in the bathroom or near water.
  • Turn off the fan periodically to prevent overheating.
  • Turn off filter fan when you leave the room.
  • Do not use while sleeping or not at home.
  • Replace filters every 3 months or when they look dirty (this depends on how frequently the unit is used).
  • Filters should have a “MERV-rating” of 13.


You can also download our fact sheet and assembly instructions below.

Fact Sheet Download Opens in new window

Assembly Instructions Download Opens in new window